Pak Prime Minister Imran Khan arrives in Iran

Pakistan Prime Minister Imran Khan Sunday arrived on his first-ever two-day official visit to Iran to promote bilateral relations, amid tensions in ties over the killing of 14 Pakistani security personnel by militants who allegedly came from the neighbouring country.

Unidentified gunmen donning uniforms of paramilitary soldiers Thursday massacred 14 security personnel, mostly from the Pakistan Navy, after forcing them to disembark from buses on a highway in the restive Balochistan province.

The victims were not initially identified and it was speculated they could be Shia Muslims and ethnic workers from Punjab, but later it emerged that they were security personnel, most of them associated with the Pakistan Navy.

Prime minister Khan's Pakistan Tehreek-i-Insaf party in a series of tweets gave updates about his visit to Iran on the invitation of Iranian President Hassan Rouhani.

"This is first visit of Prime Minister Imran Khan to Iran," the party said.

He was accompanied by Minister for Human Rights Shireen Mazari, Minister for Maritime Affairs Ali Zaidi, Adviser to Prime Minister on Commerce Razak Dawood and other officials, it said.

The Prime Minister will call on Iranian Supreme Leader Ali Khamenei, besides holding detailed consultations with President Rouhani.

He will also meet members of the Iranian and Pakistani business community in Iran.

Pakistan's relations with Iran are marked by close historic and cultural linkages and strong people to people exchanges, Pakistan Foreign Office said.

Pakistan and Iran are also members of the Economic Cooperation Organization (ECO) and Organization of Islamic Cooperation (OIC).

The Foreign Office said the Prime Minister's visit to Iran will further the close bilateral relationship between the two countries.

However, the relations received a jolt after the April 18 attack on Pakistan security personnel in Ormara area of Balochistan.

Pakistan complained that over a dozen Baloch ethnic attackers had come from the hideouts in Tehran and demanded action against them.

"Killing of 14 innocent Pakistanis by terrorist groups based in Iran is a very serious incident that Pakistan protests strongly. Pakistan awaits Iran's response to its request for action against the groups based in Iran, whose locations have been identified by Pakistan a number of times," the Foreign Office said in a protest letter to Iran.

Iranian foreign minister Javad Zarif condemned the attack, saying enemies of Pakistan-Iran ties were responsible for it.

"Strongly condemning the recent terrorist attack in Pakistan, just as PM Imran Khan embarks on his first, historic visit to Iran. Terrorists, extremists and their sponsors are terrified by close relations between Muslim states," he tweeted.

Balochistan, which borders Afghanistan and Iran, is Pakistan's largest and poorest province, rife with ethnic, sectarian and separatist insurgencies.