Iran and Pakistan have been battling insurgencies in a large swathe of desolate territory along their 900-kilometer-long shared border for decades.
The two neighbors have occasionally attempted to cooperate. But more frequently they have accused each other of sheltering militants who carry out deadly attacks on the other country.
In a major escalation, Tehran and Islamabad both launched deadly cross-border attacks this week in the worst-ever flare-up of violence involving the two countries.
The tit-for-tat strikes have plunged relations between Iran and nuclear-armed Pakistan into crisis and threatened to ignite a full-scale war in the volatile region, experts said.
"The situation after the attacks is war-like," said Kiyya Baloch, a Pakistani journalist and commentator who tracks militancy in the region. "It will have grave consequences."
Iran carried out a drone and missile attack on Pakistan's southwestern province of Balochistan late on January 16, killing two children. Tehran said it had targeted Jaish al-Adl, a Baluch militant group believed to be operating out of Pakistan.
In response, Islamabad said it conducted air strikes on January 18 in Iran's southeastern province of Sistan-Baluchistan targeting the hideouts of the Baloch Liberation Front (BLF) and the Baloch Liberation Army (BLA), two separatist groups suspected of hiding out in Iran.
Iranian officials said the strikes killed at least nine people, including six children and two women. The attack was the first time that a foreign country had launched an assault inside the Islamic republic since the devastating 1980-88 Iran-Iraq War.
Underscoring the breakdown in relations, Pakistan recalled its ambassador from Iran and blocked Tehran's envoy from returning to Islamabad.
"It is a new twist and a major diplomatic setback, which was not expected in their bilateral relations," Baloch said.
Experts said the neighbors had appeared to be improving ties after years of mutual mistrust.
Iran's Foreign Minister Hossein Amir-Abdollahian and Pakistan's acting prime minister, Anwar ul-Haq Kakar, met at the World Economic Forum in Davos, Switzerland, this week. Meanwhile, a Pakistani delegation visited Iran's southeastern Chabahar Port on January 16 in a bid to boost bilateral trade.
History Of Suspicion
Pakistan and Iran's relations have long been overshadowed by the low-level insurgencies simmering in predominately Baluch areas spanning both countries.
Pakistan's resource-rich but impoverished province of Balochistan has been the scene of a separatist insurgency and a brutal state crackdown that have killed thousands of people since 2004.
Meanwhile, separatists and militant groups operating in Sistan-Baluchistan, one of Iran's poorest provinces, carry out sporadic attacks against Iranian security forces.
Jundallah, a Baluch militant group, began carrying out bomb and gun attacks against Iranian security personnel after it was formed in 2005. After a deadly government crackdown and the execution of Jundallah leader Abdolmalek Rigi in 2010, Jaish al-Adl emerged as its successor.
Since 2013, Tehran has launched cross-border missile attacks and carried out assassinations of Jaish al-Adl leaders in Pakistan and accused Islamabad of sheltering them. In turn, Pakistan has accused Iran of supporting the BLA and BLF.
Experts said the recent cross-border strikes could prompt Tehran and Islamabad to boost their alleged support to their militant allies.
"This, in turn, will prolong and intensify the [Baluch] conflicts in these two countries," said Baloch.
A Wider War?
There have been concerns that the recent flare-up could trigger a full-blown war. But experts have played down that possibility, saying the two countries have little appetite for a costly conflict as they grapple with a litany of internal and external challenges.
"The Islamic republic has enough on its plate in the region and is overstretched," said Hamidreza Azizi, a visiting fellow at the German Institute for International and Security Affairs in Berlin. "A new war on its eastern border is the last thing they want."
Experts said Tehran has been flexing its muscles in the region since Israel, Iran's archenemy, launched a war in the Gaza Strip against Hamas, which has been designated a terrorist organization by the United States and the European Union. Hamas, which is backed by Iran, launched an unprecedented attack inside Israel on October 7.
Prior to its air raids on Pakistan, Tehran recently conducted missile attacks in Syria and Iraq's autonomous Kurdistan region. The former was seen as retaliation against the Islamic State (IS) extremist group for its deadly suicide bombings inside Iran on January 3 that killed nearly 100 people.
Pro-Iranian militant groups, including Lebanon's Hizballah and the Huthi rebels in Yemen, meanwhile, have hit Israeli and U.S. targets in the Middle East, putting the region on edge.
Azizi said Tehran's decision to hit targets in Pakistan was a miscalculation, adding Iran was not prepared for Pakistan's retaliatory attack.
"It was a grave strategic mistake by Iran to create unnecessary conflict while it is already struggling with an array of different conflicts in the region," he said.
Although experts said new strikes by Iran and Pakistan cannot be ruled out, they expected Tehran and Islamabad to pursue deescalation.
In statements issued on January 18, Tehran and Islamabad both called for good neighborly relations, even as they urged each other to tackle militancy in their territories.
China, which has ties with both Pakistan and Iran, has urged restraint. Chinese Foreign Ministry spokeswoman Mao Ning said on January 18 that Beijing "would like to play a constructive role in cooling down the situation."
"Being the main ally of Islamabad and a close partner of Tehran, Beijing is trying to calm the situation down," said Azizi.
