Kuwait on Thursday ordered the expulsion of about 15 Iranian diplomats after the emirate's top court convicted a "terror" cell of links to the Islamic republic, a government source told AFP.
Kuwait also ordered the closure of the Iranian "military, cultural and trade" missions, said the government official, who asked not to be named.
The Gulf state's supreme court last month sentenced the mastermind of the cell to life in jail and condemned 20 others to various prison terms for alleged links with Iran and Lebanese Hezbollah and plotting terror attacks in Kuwait.
State Minister for Cabinet Affairs Sheikh Mohammad Abdullah Al-Sabah, who is also acting information minister, confirmed that Kuwait had taken diplomatic action against Iran but declined to specify the measures.
"Following the supreme court ruling on the case ... the government of Kuwait has decided to take measures, in accordance with diplomatic norms and the Vienna Convention, towards its relations with the Islamic Republic of Iran," Sheikh Mohammad told AFP.
He provided no further details.
The row comes at a time when Kuwait is trying to mediate an end to the Gulf's worst diplomatic crisis in years, after Sunni-ruled Saudi Arabia and its allies cut ties with Qatar over accusations it is too close to Shiite Iran and funds extremists.
The Kuwaiti newspaper Al-Seyassah reported on Monday that 14 of the cell's 26 members had fled to Iran by sea.
They were convicted by a lower court early last year but acquitted on appeals several months later and set free.
The supreme court, whose rulings are final, overturned their acquittal on June 18 and sentenced them to between five and 15 years in prison.
Kuwait's interior ministry confirmed on Tuesday that the 14 men were on the run but it said that they had not left the country through official exit points.
The cell was busted in August 2015 and large quantities of arms, ammunition and explosives were seized from them, according to the Kuwaiti authorities.
Kuwaiti courts convicted them of working for Iran's Revolutionary Guards and Lebanese Shiite militia Hezbollah. They were also convicted of smuggling explosives from Iran.