Russia summoned the British ambassador on Thursday over Moscow’s claim that British navy personnel were involved in a Ukrainian drone attack on Russia’s Black Sea Fleet in Crimea.

Ambassador Deborah Bronnert arrived at the foreign ministry shortly after 1030 local time (0730 GMT) as a small crowd chanted anti-British slogans and held up placards reading “Britain is a terrorist state”.

Bronnert was inside the ministry for around 30 minutes, a Reuters journalist at the scene said. There was no immediate statement from either Russia or Britain on the details of what was discussed.

Russian foreign ministry spokeswoman Maria Zakharova said on Wednesday the ambassador was to be summoned over Saturday’s drone attack on Crimea, which Russia annexed from Ukraine in 2014.

Britain says the claims are false. After the drone attack, Russia temporarily suspended participation in a UN-brokered Black Sea Grain deal.

Russia casts Britain as a particularly perfidious Western power which President Vladimir Putin says is plotting to destroy Russia and carve up its vast natural resources.

After Russia invaded Ukraine, Britain, along with the United States and the European Union, imposed some of the most severe sanctions in history and supplied weapons to help Ukraine.

Russia’s defense ministry said that British navy personnel blew up the Nord Stream gas pipelines, a claim that London said was false and designed to distract from Russian military failures in Ukraine.