Fighting in Ukraine has killed at least 45 people in the last 24 hours, Kiev officials and rebel authorities said, ahead of a four-way summit in Minsk to thrash out a peace deal.

At least 19 soldiers died and 78 were wounded, military spokesman Vladyslav Seleznyov told journalists in Kiev, including five troops in a rocket attack on the east Ukrainian hub of Kramatorsk.

Another 11 people were killed in that attack, the first time rebels have struck the government's eastern military headquarters, Ukrainian President Petro Poroshenko said on his website on Wednesday.

In the rebel stronghold of Donetsk, city officials said that eight people had been killed, including five in a mortar strike on the city during the Wednesday morning rush hour.

Rebels, who rarely give a military toll, said on Tuesday they had lost seven fighters.

The leaders of France, Germany, Russia and Ukraine were to meet later Wednesday in the Belarussian capital Minsk in the hope of agreeing a peace deal to end 10 months of fighting in which at least 5,300 people have died.