"The biggest part (of troops) is still there, less than 10 percent have been withdrawn," Poroshenko told a press conference.

After a maritime conflict with Moscow in the Black Sea in late November, Poroshenko accused Russia of having sharply raised its military presence on the border, with Ukraine warning of the threat of "full-scale war."

In response, Kiev imposed martial law for 30 days in 10 regions that border Russia, the latest page of the unprecedented crisis in relations between the two neighbours.

"The threat of an invasion of Russian armed forces on Ukrainian territory still exists and we must be prepared for it," Poroshenko said, adding he sees no reason for the snap lifting of martial law.

On November 25, Russia seized three Ukrainian navy vessels and detained 24 crew members in the most dangerous incident in years between the ex-Soviet neighbours.

In 2014, Moscow annexed the Crimean peninsula from Ukraine. That move was followed by a deadly conflict in eastern Ukraine between government forces and Russian-backed separatists.

Ukraine and its Western allies have accused Russia of funnelling troops and arms across the border, but Moscow has denied the claims despite overwhelming evidence to the contrary.