Britain’s Foreign Office on Saturday said the country’s ambassador in Tehran was briefly detained by Iranian authorities during protests against the regime, and denounced the arrest as a “flagrant violation of international law”, AFP reported.

British envoy Rob Macaire was arrested for several hours in front of Amir Kabir University for inciting anti-government protestors, according to Tehran-based Tasnim news agency. A group of students reportedly gathered inside the university to protest Iran’s admission that it shot down a Ukrainian airliner. Macaire was released a few hours later and will be summoned for further explanations.

“The arrest of our Ambassador in Tehran without grounds or explanation is a flagrant violation of international law,” UK Foreign Secretary Dominic Raab said in a statement. “The Iranian government is at a crossroads moment. It can continue its march towards pariah status with all the political and economic isolation that entails, or take steps to de-escalate tensions and engage in a diplomatic path forwards,” Raab added.

EU Aviation Safety Agency urges airlines to avoid Iranian airspace

Meanwhile, the European Aviation Safety Agency on Saturday said airlines should avoid Iranian airspace until further notice. “On the basis of all available information, the recommendation in the current security climate is that overflight of Iran at all altitudes should be avoided until further notice, as a precautionary measure,” EASA said in a statement.

The existing advice not to fly over Iraq remains unchanged, EU Aviation Safety Agency said.

“This is a very dynamic situation and a new assessment will be made with the EU Commission and European Union member states early next week,” the statement added.