Kuwait has sent its first ambassador to Tehran since a downgrading of relations in 2016, Iran has announced.

Kuwait recalled its ambassador and the United Arab Emirates downgraded relations with Iran after Saudi Arabia that year cut ties with its regional rival, with Bahrain following suit.

That came after Iranian protesters attacked Saudi diplomatic missions in Iran following Riyadh's execution of Shiite Muslim cleric Nimr al-Nimr.

Badr Abdullah al-Munikh, Kuwait's new ambassador, has presented his letter of credence to Iranian Foreign Minister Hossein Amir-Abdollahian, the official IRNA news agency reported on Saturday night.

Saudi Arabia and Iran have had no diplomatic relations for six years, but have held talks, hosted by Iraq, since April last year in a bid to mend ties.

The UAE said in July it was "considering" appointing an ambassador to Tehran, which Iran said it expected "soon".

About one-third of Kuwait's local population belongs to the Shiite branch of Islam, as do most Iranians.