Two people have been detained in Poland on suspicion of attacking Leonid Volkov, an exiled top aide to the late Russian opposition leader Alexei Navalny, Lithuanian President Gitanas Nauseda told reporters on Friday.
Volkov suffered injuries from hammer blows in the attack on March 12 outside his home in Vilnius, the Lithuanian capital.
Lithuanian counterintelligence said at the time that the attack was the work of Russian special services. The Kremlin declined to comment.
Nauseda said the suspects would be transferred to Lithuania.
"I thank Poland for a really good job. I discussed this with Polish President Andrzej Duda," he said. "I also want to thank our criminal intelligence (organisation), which undertook the initial, the most important groundwork."
Volkov himself in March blamed Russian President Vladimir Putin for the attack. Before the assault he had told Reuters that leaders of Navalny's movement in exile feared for their lives.
On Friday, Volkov thanked Lithuanian police on social media platform X for working "energetically and persistently" over the past month on this case.
"I am very glad that this work has been effective", he posted. "Well, we'll find out the details soon. Can't wait to find out!"
Navalny, Putin's most prominent critic, died in February in an Arctic prison. Russian authorities say he died of natural causes. His followers believe he was killed by the authorities, which the Kremlin denies.
The office of Poland's minister in charge of special services did not immediately reply to an emailed request for comment. The Lithuanian prosecutor's office and Lithuanian police did not have an immediate comment.