Kuwait said Thursday it is shutting the Iranian cultural mission to the country and calling for a reduction in the number of Iranian diplomats stationed there, deepening a rift between the Gulf Arab states and Tehran.

The official Kuwait News Agency announced the move in a brief statement Thursday. It linked the decision to the case of a terrorist cell broken up in 2015 that authorities allege had contacts with Iran and the Lebanese Shiite militant group Hezbollah.

The Iranian ambassador to Kuwait has been notified of the decision, the news agency, known as KUNA, reported.

Iranian state television and other news agencies in the Islamic Republic quickly reported the news, citing Arab media.

Embassy staff and officials in Tehran did not immediately respond to requests for comment.

The 2015 case centers on a group of 26 people known as the al-Abdali cell whose arrests for links to Shiite powerhouse Iran touched on sensitive sectarian issues in Kuwait, a Sunni-majority country.

Besides having “furtive contacts” with Hezbollah and Iran, its members were accused of weapons possession and of planning “hostile actions” inside Kuwait, a tiny U.S.-allied Arab state wedged alongside the Persian Gulf between Saudi Arabia and Iraq.

Members of the cell have been tried and received sentences ranging from a few years in prison to, in one case, the death penalty. The latter sentence has since been reduced to life imprisonment on appeal.

Kuwait’s decision to expel the diplomats comes at a time of increased tension among the states lining the Gulf.

Saudi Arabia and its Arab allies are deeply mistrustful of Iran and many, though not Kuwait, have severed ties with it.

A group of three Gulf states plus Egypt, meanwhile, has severed ties with Qatar, accusing it of a host of misdeeds including supporting extremist groups and maintaining close ties with Iran, with which it shares a massive underwater gas field. Qatar denies supporting extremists, and says the dispute is politically motivated.

(AP)