Azerbaijan and Armenian-backed separatists in its breakaway region of Nagorno-Karabakh said on April 5 that a cease-fire was in place to halt the deadliest flare-up over that mountainous South Caucasus enclave in decades.
The apparent breakthrough comes with increasingly strident international calls for restraint between forces loyal to regional archenemies Azerbaijan and Armenia, which have been locked in conflict over Nagorno-Karabakh since the waning years of the Soviet Union.
A spokesman for the Armenian-backed Nagorno-Karabakh separatist forces, Senor Hasratyan, told RFE/RL's Armenian Service on April 5 that the mutual agreement called for an end to fighting from 12 p.m. local time.
The Azerbaijani Defense Ministry then confirmed that military operations had been stopped along the "line of contact" that effectively serves as a front line separating the combatant sides.
Armenia's Defense Ministry later said that "[o]perations along the line of contact between the Azerbaijani and Armenian forces have been suspended...upon the agreement of the parties."
The latest outbreak of violence -- the worst since the mid-1990s -- began early on April 2 and involved tanks, helicopters, and artillery.
In a statement, representatives of the so-called Minsk Group of mediators in the conflict -- France, Russia, and the United States -- urged the sides to stop fighting, saying there is no military solution to the conflict. They also called for "an immediate negotiation" on a comprehensive settlement.
"The negotiations have brought no results, but we are still prepared for the negotiating process," Azerbaijani President Ilham Aliyev said.
In Washington, the U.S. State Department welcomed the cease-fire and said it is engaging with both sides to urge them to fully respect it.
"The United States does welcome both sides confirmation of a cease-fire. It’s a very nascent cease-fire but we’re encouraged that it does seem to have taken hold," State Department spokesman Mark Toner told reporters on April 5.
"We are actively engaging with both sides to urge them to strictly adhere to the cease-fire," Toner added.
He said it was "most urgent" for both sides of the conflict to get back to the negotiating table.
In Moscow, Russian President Vladimir Putin reportedly called on the presidents of Azerbaijan and Armenia "to immediately ensure the cessation of hostilities and the observance of the cease-fire."
Putin made the appeal in separate telephone conversations with Azerbaijani President Aliyev and Armenian President Serzh Sarkisian, the Kremlin said in a statement.
"It was pointed out that Russia had been taking and would continue to take the necessary mediating steps aimed at normalizing the situation," the statement said.
Moscow "will continue making all necessary intermediary steps to normalize the situation in connection with the Nagorno-Karabakh conflict," it added.
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Earlier in Paris, French Foreign Minister Jean-Marc Ayrault said the co-chairs of the Minsk Group would send envoys to Azerbaijan, Armenia, and to Nagorno-Karabakh in a bid to resolve the crisis.
The announcement came with representatives of the so-called Minsk Group of mediators in the conflict -- France, Russia, and the United States -- expected to meet in Vienna on April 5 for crisis talks.
Ayrault was speaking after talks with his German counterpart, Frank-Walter Steinmeier, who said the Organization for Security and Cooperation in Europe (OSCE) would send a fact-finding mission to Azerbaijan, Armenia, and Nagorno-Karabakh.
After speaking with the Azerbaijani and Armenian foreign ministers -- Elmar Mammadyarov and Edward Nalbandian respectively -- EU foreign-policy chief Federica Mogherini urged a strict observance of the cease-fire by all parties and an end to any targeting of civilians.
"All parties must take the necessary steps to create an environment conducive to successful negotiations, including avoiding actions and statements which could further complicate the already complex environment," Mogherini's statement said.
Populated mainly by ethnic Armenians and with many ethnic Azerbaijanis having already fled, the territory declared independence from Azerbaijan in a 1988-94 war that claimed an estimated 30,000 lives and displaced hundreds of thousands of people.
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Each side reported new casualties on April 5 as the death toll from four days of fighting rose above 40, with one estimate as high as 64 killed.
Azerbaijan has reported 16 combat deaths, while the Karabakh military said 20 of its servicemen had died.
The Armenian Defense Ministry later announced that seven people were killed in an Azerbaijani drone attack on a bus carrying volunteers to the disputed region.
Azerbaijan also reported civilian deaths, including at least four overnight.
The destruction of heavy military equipment has been claimed by both sides.
Each side accused the other of escalating the violence as the West, Russia, and neighbor Iran appealed to all sides for restraint.
On April 4, Azerbaijani Defense Minister Zakir Hasanov warned that Baku's forces would begin an artillery barrage on Stepanakert, which has around 50,000 residents, if Armenian forces did "not stop shelling our settlements."
The defense forces of the unrecognized Nagorno-Karabakh republic promised a "very painful" response.
WATCH: Azerbaijani Power Station Destroyed Ahead Of Nagorno-Karabakh Cease-Fire
They also said Azerbaijan "had been increasing the caliber of its weapons day by day," and had used Smerch multiple-launch rocket systems to shell civilian settlements and military targets.
Azerbaijan's Defense Ministry on April 5 denied having targeted civilians and a spokesman said that while Baku's forces had Smerches, they hadn't used them "so far."
Baku also said the Armenians were using large-caliber machine guns and 120-millimeter mortars overnight.
Armenian President Serzh Sarkisian warned on April 4 that a further escalation of the fighting would be fraught with "unpredictable and irreversible consequences, including a full-scale war."
Armenian foe and NATO member Turkey waded in on April 5 to say it was "standing side-by-side with our brothers in Azerbaijan."
"This persecution will not continue forever," Turkish President Recep Tayyip Erdogan said. "Karabakh will one day return to its original owner. It will be Azerbaijan's."
Turkish Prime Minister Ahmet Davutoglu condemned what he described as Armenian attacks in the Nagorno-Karabakh region and vowed Ankara would stand by Azerbaijan.
U.S. Secretary of State John Kerry and Russian Foreign Minister Sergei Lavrov expressed serious concern over an escalation in the standoff and called for a swift cessation in fighting.
U.S. Vice President Joe Biden said via Twitter he had told Sarkisian and the president of Azerbaijan, Ilham Aliyev, that "a comprehensive settlement in Nagorno-Karabakh is critical for their stability, security, prosperity."
