UK envoy to Tehran Rob Macaire was temporarily was detained as an unidentified foreign national participating in an unlawful gathering held in front of Tehran Amir Kabir University on Saturday night.

Macaire, who was arrested while taking pictures of the protests, was immediately released after his identity was checked and approved by the police.

EU Foreign Policy Chief Josep Borrell in a Sunday tweet wrote, “Very concerned about the UK envoy being detained @HMATehran in Iran. Full respect of the Vienna convention is a must. The EU calls for de-escalation and space for diplomacy.”

A group of students had gathered inside the university to voice their protest after Iran announced the unintentional downing of a Ukrainian plane.

The General Staff of the Iranian Armed Forces announced on Saturday that the country’s air defense unintentionally shot down a Ukrainian passenger plane on January 8 amid the highest level of readiness because of a possible military attack by the US.

According to IRNA, Iranian Foreign Ministery has objected to the UK’s envoy act and is waiting for the police report on the details.

The UK Foreign Ministry has also objected to the detention of its ambassador to Tehran and called it against international law.