Iran and Pakistan are at loggerheads over cross-border attacks, with both sides accusing the other of turning a blind eye to militants operating within their territory.
Tensions between Tehran and Islamabad are at an all-time high after the two neighbors launched formal diplomatic protests to condemn recent attacks and clashes along the 900-kilometer border they share.
On October 18 Iran summoned Pakistani ambassador in Tehran to demand Islamabad stop "terrorists and rebels" from crossing into Iran’s southeastern province of Sistan-Baluchistan, which borders Pakistan's southwestern province of Balochistan.
The same day, Pakistani officials told the Iranian envoy in Islamabad that they strongly protest what they claim was an incursion by Iranian border guards that allegedly killed one Pakistani security official on October 17.
Officials and media in both countries claim at least two Iranian border guards were also killed in the same clash in the Kech district of Balochistan near the Iranian border.
Days earlier, at least five policemen were killed in the border area of Saravan in Sistan-Baluchistan in an ambush on a police outpost on October 8 and a car bomb on October 9. The next day, seven people, including three senior Iranian police officials, were killed in a plane crash near the provincial capital, Zahedan. They were traveling to the region to investigate the previous attacks.
Tehran said the crash was an accident, but Sistan-Baluchistan has been the scene of militant attacks, including suicide bombings and ambushes, that have killed hundreds of civilians and soldiers since 2005.
Shahzada Zulfiqar, a journalist in Quetta, the capital of Balochistan, says the border management mechanism the two neighbors agreed on last year to stop terrorist attacks and smuggling appears to have failed.
"The recent alleged attack by Iran inside Pakistan was a warning," he told RFE/RL's Gandhara website. "Tehran is worried over the continued presence and emergence of new militant groups in Balochistan, which it sees as ultimately detrimental to its interests and posing a persistent security threat."
Zulfiqar says for years Tehran's Shi'ite clerical regime has complained to Islamabad about Sunni Baluch rebels who it claims have used the border districts of Chaghai, Washuk, Kharan, Panjgur, and Kech to launch cross-border attacks into Sistan-Baluchistan, which the rebels profess is their homeland.
"Iran is not convinced that these insurgents are living in fear in Pakistan," he said. "I believe that they know where these rebels are hiding inside Balochistan and this prompts their actions."
Zulfiqar says Iran's erstwhile Sunni Baluch rebel group Jundallah split into three factions after Tehran hanged its leader Abdulmalik Rigi in 2010, and that rebels now operate under the banner of Jundallah, Jaysh al- Nasr and Jaysh al-Adl.
"Elements within the Jaysh al-Adl and Jundallah have now partnered with some locals [in Balochistan] to form Lashkar-e Khurasan, which is trying to dominate politics in Balochistan's districts along the border with Iran," he said.
Lashkar-e Khurasan is believed to be led by Mullah Omar, a Sunni militant leader from Sistan-Baluchistan who is not related to the Afghan Taliban leader. He was the former leader of Jaysh al-Adl.
"They [Lashkar-e Khurasan] have demanded that the Zikri Muslim sect and Hindus embrace Sunni Islam or face death," Zulfiqar said.
Lashkar-e Khurasan's apparent strength troubles Iran deeply, as do Sunni extremist factions in Syria and Iraq.
Abdollah Araghi, a senior commander of Iran's Islamic Revolutionary Guards Corps, told Iranian state television on October 18 that Tehran has proof that militants are lunching cross-border attacks in Sistan-Baluchistan from Pakistan.
A few days earlier, Iranian Brigadier General Hussein Salami warned Islamabad that Iranian troops could enter Balochistan to "prevent terrorists" from coming into Iran.
The tone in Quetta and Islamabad is equally strident. Khan Wasay, a spokesman for the paramilitary Frontier Corps in Balochistan, accused Iran of killing one if its soldiers in an "unprovoked cross-border attack" on October 17. He said 30 more Iranian border guards had entered Pakistani territory the same day and held locals hostage for six hours in the remote Naukundi region.
Major General Ejaz Shahid, head of the Pakistani Frontier Corps, warned the same day that his forces will respond to future cross-border incursions from Iranian forces.
Balochistan is an extremely sensitive region for Islamabad. For more than a decade, Pakistani forces have battled against secular Baluch separatist rebels who are waging their fifth insurrection in Pakistan's 67-year history. Thousands of civilians have died in the rebel attacks and military operations as both sides accuse each other of grave human rights abuses.
The Pakistani government has not publicly accused Iran of supporting the Baluch separatists. But Zulfiqar said some Pakistani observers claim that the secular Baluch rebels enjoy a degree of impunity across the border in Iran’s Sistan-Baluchistan province.
Balochistan's estimated 10 million people have paid a high price for the insecurity. A recent report by the nongovernmental Human Rights Commission of Pakistan said reports that more than 300,000 civilians have fled Balochistan during the past decade.
These include large numbers of Balochistan's tiny Shi'ite and Hindu minorities.
Since 2004, more than 1,000 Hazaras have been victims of attacks, many of which the hardline anti-Iran Sunni faction Lashkar-e Jhangvi have claimed responsibility for.
Zulfiqar said that the sectarian violence in the region is connected to the larger conflict between the Shi'ite and Sunni powers in the Middle East. He says Sunni extremist organizations are on the rise in Balochistan, particularly in the districts along a major road that connects the provincial capital Quetta to the Iranian border.
"Quetta, Mastung, Naushki, and Chagai appear to be flashpoint of this sectarian conflict," he said. "These groups definitely have links to the Islamic State militant group now active in Iraq and Syria."
Balochistan's most senior elected civilian leader, Chief Minister Abdul Malik Baloch, told Pakistan's daily "Dawn" earlier this month that he "cannot rule out the presence of Islamic State militants in Balochistan."
Zulfiqar anticipates myriad complications if Tehran and Islamabad fail to quickly resolve the border problem.
"The coming time will be more dangerous for the common people along the border between the two countries," he said.