Jailed Kremlin critic Alexei Navalny has called on Russians to stage daily protests against Moscow's invasion of Ukraine, depicting President Vladimir Putin as an "obviously insane tsar."

Navalny called for protests across the country and abroad to signal that not all Russians support the war and show solidarity with the thousands of people detained in anti-war protests in Russia since last week's invasion.

"We cannot wait even a day longer. Wherever you are. In Russia, Belarus or on the other side of the planet. Go out onto the main square of your city every weekday at 19.00 and at 14.00 at weekends and on holidays," he said in a statement published on Twitter by his spokesperson.