Prime Minister Imran Khan reached Iran on Sunday evening for a two-day official visit on the invitation of Iranian President Hassan Rouhani.

This marks the first time Prime Minister Imran is visiting the neighbouring country after assuming office.

The premier made a stopover in Mashhad before proceeding on to Tehran. Ali Reza Razm Hussaini, the governor general of Khorasan-e-Razavi province, received the prime minister upon arrival at the Shahid Hasheminejad International Airport.

Ambassador of Pakistan to Iran Riffat Masood, officials of the Pakistan Embassy in Tehran and Pakistan Consulate in Mashhad were also present at the airport.

According to a press release by the Prime Minister's Office, the premier is accompanied by Minister for Human Rights, Dr Shireen Mazari; Minister for Maritime Affairs, Syed Ali Haider Zaidi; Adviser to PM on Commerce, Abdul Razak Dawood; Special Assistant to the Prime Minister on Overseas Pakistanis and Human Resource Development, Sayed Zulfiqar Abbas Bukhari; Special Assistant to the Prime Minister on National Health Services, Dr Zafarullah Mirza; and Special Assistant to the Prime Minister on Petroleum, Nadeem Baber.

Later in the day, the premier visited the shrine of Imam Raza in Mashhad.

After a brief stopover in Mashhad, Prime Minister Imran arrived at Tehran's Mehrabad Airport, where he was received by Health Minister of Iran (Minister-in-waiting) Dr Saeed Namaki.

"He was presented 'static guard' upon arrival," read a press release issued by the PM Office.

Prime Minister Imran was initially scheduled to visit Iran in January, but the visit was postponed at the eleventh hour because of unexplained reasons.

Relations between Iran and Pakistan have had a bad patch due to security issues along the border.

On Saturday, the Ministry of Foreign Affairs (MoFA) lodged a strong protest with Iran regarding its inaction against terror groups believed to be involved in the Ormara massacre that saw 14 armed officers murdered in cold blood on the Balochistan coastal highway at Buzi Top.

In a letter written to the Iranian embassy on Friday, the MoFA stated: "Killing of 14 innocent Pakistanis by terrorist groups based in Iran is a very serious incident that Pakistan protests strongly."

A day earlier, Iranian Foreign Minister Mohammad Javad Zarif had condemned the attack.

In a post shared on Twitter, Zarif wrote: "Strongly condemning the recent terrorist attack in Pakistan, just as PM [Imran Khan] embarks on his first, historic visit to Iran."

According to diplomatic sources, border security issues will be on top of the prime minister's agenda in Tehran.