A hammer-wielding assailant attacked Leonid Volkov, a Navalny aide, outside his home in Vilnius, Lithuania, in March, breaking his arm and pounding his leg with a series of blows.

Lithuania's counter-intelligence service accused Russia's intelligence services of being behind the attack. The Kremlin declined to comment but said people should respect and listen to President Vladimir Putin rather than be afraid of him.

Yulia Navalnaya, who lives outside Russia and has said she will take up her husband's battle against Putin, said the incident had prompted her to increase her personal security measures.

"We have thought about some new security protocols. To be honest, I don't really like to go around with a bodyguard," Navalnaya, who was speaking in Vilnius, told Time.

"Alexei and I never had security, and I think I inherited some of that courage, that cavalier attitude from Alexei. But when you're too cavalier, you can make a wrong move. So, for now, my colleagues have asked me to go around with a bodyguard.

"We don't know what will come next, and taking such risks is definitely not a good idea."

Navalny, Putin's most prominent domestic critic, died in February in an Arctic prison. Russian authorities, who have outlawed Navalny's movement as extremist, say he died of natural causes. His followers believe he was killed by the authorities, which the Kremlin denies.

(Reporting by Andrew Osborn; Editing by Gareth Jones)