MOSCOW -- Russian opposition politician Aleksei Navalny has been summoned for questioning in a criminal case launched over comments he made on social media.

Navalny wrote on Instagram that he was handed a subpoena when he was leaving his Moscow apartment on July 14.

He did not say exactly when he was ordered to show up at the Investigative Committee for questioning.

The Investigative Committee said in mid-June that Navalny had been accused of libeling a World War II veteran who featured in a video clip with other Russians to express support for proposed constitutional reforms.

In a social media post on June 2, Navalny, one of President Vladimir Putin's most vocal critics, described those in the video as "traitors," "people with no conscience," and "corrupt lackeys."

The Investigative Committee said the comments contained 'deliberately false information denigrating the honor and dignity' of the WWII veteran.

Navalny faces penalties ranging from a fine of 1 million rubles ($14,255) to 240 hours of community service if convicted.

Earlier this year, Russian state-run media broadcast videos of WWII veterans, celebrities, and ordinary people expressing their support for constitutional amendments that were approved by a national vote on June 25-July 1.

Among other changes, the amendments allow Putin to seek two more presidential terms after his current second, consecutive presidential term ends in 2024.

Navalny, 44, has been jailed several times in recent years, barred from running for president, and had a bid to run for Moscow mayor blocked.

In March, Navalny and his associate Ivan Zhdanov said that their bank accounts had been emptied and all their payment cards and those of relatives been blocked in what they described as a move to discredit and disgrace them.

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