VILNIUS, Lithuania (AP) — Two men have been detained in Poland on suspicion that they attacked Russian activist Leonid Volkov — an ally of the late opposition leader Alexei Navalny — on the orders of foreign intelligence services, officials said Friday.

Volkov was attacked on March 12 outside his home in the Lithuanian capital, Vilnius, where he lives in exile. The attacker smashed one of his car’s windows, sprayed tear gas into his eyes and hit him with a hammer, police said at the time.

Lithuanian President Gitanas Nausėda announced the arrests to reporters in Vilnius and thanked Poland for its work.

“Two people have been detained in Poland on suspicion of beating Russian opposition leader Leonid Volkov. I thank the Republic of Poland for the excellent work it has done. I have discussed this with the Polish president and thanked them for their excellent cooperation,” Nausėda said.