Pakistan's Prime Minister Imran Khan arrived in neighbouring Iran for bilateral talks, a day after Islamabad urged Tehran to act against armed groups behind the killings in Pakistan's Balochistan province earlier this week.
Khan began his official two-day visit to Iran, the first since he took office last year, with a stop in the northeastern holy Shia city of Mashhad on Sunday.
Khan will meet Iran's Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani, as well as other officials in Tehran on Monday.
"During the meetings, improving bilateral ties, border security, countering terrorism and regional issues will be discussed," Iranian state TV said.
A statement by Pakistan's foreign ministry said relations between the two countries are "marked by close historic and cultural linkages and strong people to people exchanges".
"The prime minister's visit to Iran will further strengthen the bilateral relationship between the two countries," it added.
Border security
Ties between Iran and Pakistan have been strained in recent months, with both sides accusing each other of not doing enough to stamp out armed groups allegedly sheltering across the border.
A new umbrella group representing various armed groups operating in Pakistan's southwestern Balochistan province claimed responsibility for an attack on Thursday when 14 passengers were killed after being kidnapped from buses in the province, which borders Iran.
Shah Mahmood Qureshi, Pakistan's foreign minister, said on Saturday the training and logistical camps of the new alliance that carried out the attack were inside Iran and called for Tehran to take action against the fighters.
Meanwhile, predominantly Shia Muslim Iran says armed groups operate from safe havens in Pakistan and has repeatedly called on Islamabad to crack down on them.
Tehran has stepped up security along its long border with Pakistan after a suicide bomber killed 27 members of Iran's elite Revolutionary Guard in mid-February in southeastern Iran, with Iranian officials saying the attackers were based inside Pakistan.
The Sunni group Jaish al-Adl (Army of Justice), which says it seeks greater rights and better living conditions for the ethnic Baloch minority, claimed responsibility for that attack.
