Leonid Volkov, a close ally of late Russian opposition leader Alexei Navalny, promised in a BBC interview aired Saturday to "never give up" fighting against President Vladimir Putin despite recently being attacked outside his home.

Navalny died in an Arctic prison in February, which Volkov blamed directly on Putin.

In his first television interview since March's hammer attack outside his home in Lithuania, Volkov told BBC's "Sunday with Laura Kuenssberg" that Navalny "asked us to never to give up and to continue our work... to defeat Putin and to build this beautiful Russia of the future."

Doing so was the "only practical way to preserve his legacy and to make his ultimate sacrifice not to be in vain," said Volkov, in extracts of the video link interview aired on Saturday.

He called Navalny a "great guy, inspiring personality, a true hero and a great and very capable political leader" whose death was an "open wound in our hearts" and who could not be replaced.

But the task of the opposition movement was now to support Navalny's wife Yulia as its new "charismatic leader," he added.

Volkov said that during the attack, someone broke a car window and sprayed tear gas in his eyes before hitting him with a hammer.

Navalny's allies shared photos showing Volkov's injuries, including a black eye, a red mark on his forehead and bleeding on his leg.

Volkov worked as the late leader's ex-chief of staff and as chair of his Anti-Corruption Foundation until 2023.