Massive rallies in Ukraine have evolved into a revolution, according to leader of the Third Ukrainian Republic movement, ex-Interior Minister and one of opposition leaders Yuriy Lutsenko.

"Our plan is clear: It is no longer a rally, or action. It is a revolution," he told demonstrators who are chanting "Revolution!" during the popular assembly on Independence Square in Kyiv on Sunday.

Civil society and politicians are completing today what was not finished during massive protests in 1991 and 2004, he said. "The Ukrainian Soviet Socialist Republic is dying here today. We are witnessing its funeral," he said.

Lutsenko urged Ukrainians from the eastern regions to join other regions in the fight against the regime. "It's not the president we're changing now, it's the system of power in the country. We are changing Ukraine!" he said.

Lutsenko urged participants in the popular assembly to gather on Independence Square, near the Cabinet and presidential administration buildings on Monday.

He also said that the interior minister had to be prosecuted after the dispersal of the Euromaidan rally for European integration.

Hundreds of thousands of people have filled Independence Square, according to the organizers. Journalists say there are at least 100,000 people there.