Two soldiers, a pro-Russian rebel and a civilian were killed in 24 hours of fighting in eastern Ukraine.

Two soldiers, a pro-Russian rebel and a civilian were killed in 24 hours of fighting in eastern Ukraine, the Ukrainian military and rebels said separately on Sunday.

"We have lost two soldiers in fighting and acts of provocation, five have been wounded," Ukraine army spokesman Andriy Lysenko told journalists, reporting heavy shelling by rebels despite a four-month truce.

Senior separatist figure Eduard Bassurin, meanwhile, said shots "fired by the Ukrainian army" killed a rebel and a civilian.

Lysenko accused rebels of using "on 10 occasions artillery over 100 mm calibre." Such heavy weaponry was to have been withdrawn from the frontline under the terms of a peace deal signed in Minsk.

The military spokesman said firing came from the area around Donetsk airport, controlled by pro-Moscow rebels since January but still a flashpoint, as well as close to the village of Trokhizbenka in the rebels' self-proclaimed people's republic of Lugansk.

Also Sunday, Ukrainian President Petro Poroshenko charged that a "record number" of Russian troops were deployed at the border with Ukraine, without giving a precise figure.

"These reports from our intelligence services have been confirmed by NATO, the United States and the European Union," Poroshenko told Ukrainian television.

He added that the Ukrainian army, which has deployed some 64,000 soldiers in the conflict zone as well as interior ministry forces, was prepared to "defend Ukraine".

More than 6,500 people, most of them civilians, have been killed in the conflict, which began in April 2014.