KIEV (Reuters) – A Ukrainian military counterintelligence officer was seriously wounded after Russian aircraft fired missiles at Ukrainian vessels in their encounter on Sunday, the head of Ukraine’s state security service (SBU) said.

Ukraine and Russia have traded accusations after Russia seized three Ukrainian ships after firing on them on Sunday. The clash prompted Ukraine to introduce martial law, citing the threat of a Russian land invasion.

“According to the confirmed operational information of the SBU, one of the Russian attack aircraft used two unguided combat missiles against the Ukrainian boats, as a result of which one of the officers of the SBU was seriously wounded,” Vasyl Hrytsak said in a statement on Monday.