WARSAW (Reuters) -A Polish court ruled on Friday that one of the two men suspected of attacking an exiled top aide to late Russian opposition leader Alexei Navalny could not be extradited to Lithuania.

The former aide, Leonid Volkov, suffered injuries from hammer blows in the attack on March 12 outside his home in Vilnius, the Lithuanian capital.

Polish authorities arrested two men in April in response to a European arrest warrant issued by Lithuania and agreed to hand them over for a criminal prosecution.

An appeals court in Poland said on Friday that one of the men could not be sent to Lithuania as there were similar proceedings being conducted by Polish prosecutors. The court's decision regarding the other man is still pending.

The two suspects, detained in Warsaw on April 3, arePolish citizens. They had been charged in Lithuania with intentionally causing minor bodily harm to Volkov becauseof his beliefs, which is punishable by a fine or a jail term.

Volkov has blamed Russian President Vladimir Putin for the March attack on him.

Navalny died in February in a Russian Arctic prison. Russian authorities say he died of natural causes. His followers believe he was killed by the authorities, which the Kremlin denies.

(Reporting by Barbara Erling, Writing by Anna KoperEditing by Gareth Jones)