The attack on a close ally of late Russian opposition leader Alexei Navalny was likely organised and executed by Russia, according to Lithuanian counterintelligence.
Police said Leonid Volkov was attacked with tear gas and a hammer as he arrived at his home in the Lithuanian capital of Vilnius yesterday.
The assault was likely carried out by Russia - and could be linked to the Russian presidential election, Lithuania's state security department has said.
Mr Volkov earlier accused Vladimir Putin's "henchmen" of being behind the attack, and said in a video that it was a "typical gangster greeting" from the Russian president.
