Iranian embassy staff in the Albanian capital worked through the night after they were given 24 hours to leave the country over a major cyberattack that the Albanian government blames on Iran.

It is the first known case of a country cutting diplomatic relations over a cyberattack.

Movement inside the Iranian embassy in Tirana continued nonstop from Wednesday into Thursday. An empty barrel was seen taken into the compound and later a fire was started in it, apparently burning documents. A diplomatic car went in and out, while an Albanian police officer communicated with the embassy before two officers entered and left after a few minutes.

The staff have until noon (1000 GMT) Thursday to leave Albania.

On July 15, a cyberattack temporarily shut down numerous Albanian government digital services and websites. Prime Minister Edi Rama said Wednesday that there was “undeniable evidence” that the Iranian government was behind the attack.

The United States supported the move by Albania, a NATO member, and vowed unspecified retaliation against Iran for what it called “a troubling precedent for cyberspace.”

Iran condemned the diplomats’ expulsion, calling the action ill-considered and short-sighted, according to Iranian state TV.

In a statement, the Iranian Foreign Ministry denied Tehran was behind any cyberattack on Albanian government websites, adding that it’s Iran which is a target of such attacks on its critical infrastructure.

Ties between Iran and Albania have been tense since 2014 when Albania sheltered some 3,000 members of the Iranian opposition group Mujahedeen-e-Khalq, or MEK, who had left Iraq.

In July, MEK had planned to hold the Free Iran World Summit in Manez, west of Tirana, with U.S. lawmakers among the invitees. The meeting was canceled “for security reasons and due to terrorist threats and conspiracies.”

In two separate instances in 2020 and 2018, Tirana expelled four Iranian diplomats for “threatening national security.”