Tensions in the Balkans are on the rise, unnerving some who fear that increased nationalism, ethnic rivalries, and weak democratic institutions -- mixed with sluggish economies -- could be a recipe for deeper crisis and possibly even violence.
Kosovo's largest opposition party is pushing for a referendum to unite with Albania, even though such a move is prohibited by the fragile former Yugoslav province's constitution. Meanwhile, ethnic Serbs in Bosnia-Herzegovina are talking about an independence referendum.
Belgrade and Skopje are the scenes of nightly protests as a familiar mix of political instability, territorial disputes, and ethnic rivalries threatens to reignite the restive region.
But stopgap solutions imposed since the mid-1990s to bring stability and security in the Balkans, a conflict flash point for just over a century that has a history of dragging the world's superpowers into war, are crumbling.
This has left Moscow, Brussels, and Washington in a race for influence, while Turkey, on the eastern edge of the Balkans, is strengthening historic ties with the region's Muslims, adding to the undercurrent of growing uncertainty.
In all, 18 disputes, many over autonomy and secession, can currently be observed in the Balkans, according to the Heidelberg Institute for International Conflict Research, threatening to undo the fragile peace that has held since the Dayton agreement of 1995 ended the Bosnian War.
Here are the main issues that threaten to bring tensions in the region to a boil:
Religious/Ethnic Strife
For more than four decades following World War II, Josip Broz Tito used the concept of "brotherhood and unity" to weave Croats, Slovenes, Serbs, Bosnians, Kosovars, Montenegrins, and Macedonians into a tight fabric called Yugoslavia.
But more than a quarter-century ago, that country frayed and a series of wars between ethnic groups that left tens of thousands dead tore Yugoslavia apart at the seams.
The brutal violence degenerated into "ethnic cleansing" and turned Muslims, Roman Catholics, and Orthodox Christians against each other. Some pockets of Islamist extremism have even formed in the region.
Memories of the conflict linger, and tensions continue to flare up just below the surface of the peace.
In January, a train dispatched from the Serbian capital toward Mitrovica -- an ethnically divided city in predominantly Serb-populated northern Kosovo -- was stopped just before reaching the countries' shared border. Its abortive journey unleashed a torrent of nationalist anger and a flurry of diplomacy to avoid conflict between Serbs and ethnic Albanians, who represent a majority in Kosovo.
Kosovo refused to allow the Serbian train to cross the border.
In Macedonia, December elections have failed to end two years of political stalemate, with President Gjorge Ivanov refusing to give the mandate to form a government to Social Democrats allied with ethnic Albanian parties, ostensibly because the latter seek more rights and the establishment of Albanian as Macedonia's official second language. Ethnic Albanians make up about 25 percent of the country's 2.1 million inhabitants.
Ivanov has argued that the language issue is part of an attempt to destroy Macedonia's independence, and he has accused Albania of interference in Macedonian affairs.
In a sign of Macedonia's mounting instability, about 200 protesters, some wearing black ski masks, stormed parliament on April 27 and assaulted several lawmakers. The violence later spilled out onto the streets of Skopje.
One of their main targets, Social Democratic Union leader Zoran Zaev, was left with blood streaming down his face from a gash on his head and several other deputies were also injured after the coalition approved Talat Xhaferi, an ethnic Albanian, as the new parliament speaker.
WATCH: Protesters Storm Macedonia's Parliament
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Protesters Storm Macedonian Parliament
Indeed, the question of ethnic Albanians, who comprise about 8 million people including some 1.5 million in Kosovo,* may be the biggest flash point.
After Kosovar President Hashim Thaci told RFE/RL on April 19 that "all Albanians in the region will live in a single country in order to proceed further with the integration into the European family," fears have grown that Albanians in the region, along with ultranationalists in Tirana, will trigger armed conflict by pushing the concept of a Greater Albania.
"Although it is a relatively small area geographically, there are a large number of long-standing and very virulent conflicts in the Balkans. Above all, the many ethnic conflicts that we have observed in the Balkans over the years, even decades, have not decreased in number. Our assessment is that the potential for conflict in the Balkans remains significant," according to Silvia Steininger of the HIIK.
EU Membership
After the breakup of Yugoslavia, democratic processes were driven in large part by the prospect of joining the European Union. Slovenia was the first ex-Yugoslav republic to join the bloc in 2004, followed by Croatia in 2013.
But the tough reforms required to shed decades of communist rule and bring economies shattered by civil wars in line with the bloc have hit ordinary citizens in the region hard, prompting many to sour on accession.
In Serbia, which applied to join the EU in December 2009 and hopes for accession by 2020, support for membership was at 47 percent in February compared with a peak of 73 percent in November 2009.
Making matters worse, a rise in nationalist, anti-immigrant sentiment within the bloc itself appears to have dampened EU enthusiasm to welcome new members from the Western Balkans.
More recently, there have been mixed U.S. signals to the region under President Donald Trump, such as in February when Dana Rohrabacher, a Republican who chairs the House Committee on Foreign Affairs, said that "Macedonia is not a country," arousing fury from Skopje.
Concern is growing within the EU of a potential failure to quell "extremely dangerous" ethnic tensions within or between nations in the Balkan countries in a region that is also exposed to "global tensions."
"If we [the EU] leave them alone -- Bosnia-Herzegovina, Republika Srpska, Macedonia, Albania, all those countries -- we will have war again," European Commission President Jean-Claude Juncker told visiting U.S. Vice President Mike Pence in Brussels in February.
Russian Influence
If the EU was seen as a pillar of stability, Russia is now being touted as the possible wrecking ball.
Officials in Podgorica have accused Russia of involvement in an alleged coup plot late last year purportedly aimed at impeding Montenegro's further Western integration. Moscow rejects the allegation.
A traditional Slavic ally, the Kremlin has friends across the Balkans and a rival seeking influence as well: the United States.
Aleksandar Vucic won a presidential election earlier this month in Serbia while pushing for closer ties to Moscow, even meeting with Russian President Vladimir Putin in the waning days of the campaign.
Seemingly keen to gain influence and drive a wedge between the West and the region, Moscow has already given Serbia weapons and military equipment, including a promise of six MiG-29 warplanes.
Russian President Vladimir Putin (left) meets with Serbian Prime Minister Aleksandar Vucic at the Kremlin in Moscow on March 27.
Russia reacted sharply to the U.S. ratification of Montenegro's entry into the NATO security alliance on April 11, saying it "reflects the logic of confrontation on the European continent and creates new dividing lines."
In November, the Kremlin backed a referendum in part of Bosnia, Serb-majority Republika Srpska, on a separate Bosnian Serb national day even though it had been banned by the courts.
"What Putin wants in the Balkans seems plain enough -- namely political chaos that will distract the West, which made itself the region's ward in the 1990s," John Schindler, a security expert and former National Security Agency analyst and counterintelligence officer, wrote in The Observer.
"Kremlin saber-rattling in 2017 to test the [NATO] alliance's resolve may instead come in the Balkans, where states are weak and Western control looks shaky.... [T]he United States and our European allies need to urgently calm down Southeastern Europe before its problems get out of hand and mass violence returns to that perennially troubled region."
Corruption
An old saying goes, "We don't have corruption because we are poor; we are poor because we have corruption."
Despite attempts at public-sector, private-sector, and judicial reforms, that phrase resonates today in the Balkans as much as it ever has.
Nowhere is that more evident than in the recent Serbian presidential election, when a satirist ran as a candidate who boasted of being a caricature of all of the worst qualities of the country's politicians.
Saying he holds a fake university degree, has wealth he can't account for, and is willing to make promises he can't keep, 25-year-old Luka Maskimovic ran as Ljubisa "Beli" Preletacevic and finished third in the voting with almost 10 percent.
Since the election, nightly demonstrations across Serbia have attracted thousands protesting against Vucic's victory, calling him a "thief" who "stole" the result through the muzzling of the media, voter intimidation, and bribery.
According to a survey late last year by Transparency International, 65 percent of Kosovars thought corruption was one of the three biggest problems their country faced. In Bosnia, the number was 55 percent, while it was 39 percent in Serbia and 34 percent in Macedonia, which has a special prosecutor's office for corruption cases. So far, only 11 have been brought forth, none of which has gone to court.
"As long as those who abuse their positions of power remain unpunished and there is general impunity for their actions, however, there will be no trust in the legal system and no popular support for reforms," according to Andy McDevitt, who authored Transparency International's Fighting Corruption In The Western Balkans And Turkey report late last year.
"It is equally critical to ensure that the positive reforms achieved so far are not reversed, as has been the case all too often in the region."
* CORRECTION: This story has been amended from an earlier version to note that there are 1.5 million ethnic Albanians in Kosovo.