Pakistan Prime Minister Imran Khan left for Tehran on Sunday on a day-long visit to help mitigate tensions between bitter regional rivals Iran and Saudi Arabia.

Tension has been simmering between the two countries ever since the start of attacks on Yemen in 2015 by a coalition-led by Riyadh and execution of a prominent Shia cleric in the Gulf Kingdom in 2016.

Iran and Saudi Arabia came close to blows after damaging September 14 attack on oil facilities in the Gulf Kingdom. Saudi and its allies blamed Iran for the attack, a charge which Tehran denied.

On October 11, an Iranian-owned oil tanker was hit in Red Sea waters off the Saudi coast.

"As part of his initiative to promote peace and security in the region, Prime Minister Imran Khan will be undertaking a visit to Iran on October 13," the Foreign Office (FO) said.

It said that during the visit, the Prime Minister Khan will have meetings with the Iranian leadership, including supreme leader Ayatollah Ali Khamenei and President Hassan Rouhani.

Besides issues relating to peace and security in the Gulf, bilateral matters and important regional developments will be discussed, the FO said.

It will be the Prime Minister's second visit to Iran this year.

Khan is accompanied by Foreign Minister Shah Mahmood Qureshi and Special Assistant to the Prime Minister on Overseas Pakistanis and Human Resource Development Sayed Zulfiqar Abbas Bukhari.

Khan had a bilateral meeting with President Rouhani on the sidelines of the UN General Assembly session in New York in September.

Diplomatic sources said that officials from Pakistan visited both Iran and Saudi Arabia ahead of Khan's visit to pave ground for his mediatory role.

They said Khan was expected to visit Saudi Arabia on Tuesday to convey the developments regarding his meetings with the Iranian leadership.

Khan said in September that he was also asked by President Donald Trump to play a role in reducing tension between the two countries.

Pakistan has been trying to improve ties between Iran and Saudi Arabia due its close ties with both nations.

Former premier Nawaz Sharif also visited the two capitals in 2016 to seek reduction in their differences.