A pro-Russian separatist fighter stands on Monday in Uglegorsk, six kilometers southwest of the transport hub of Debaltseve. The European Union on Monday put fresh sanctions against Moscow on hold ahead of a summit to thrash out a Ukraine peace plan aimed at ending 10 months of bloodshed. Photo: AFP

A rocket attack on Ukraine's military headquarters in its war-torn east killed at least six civilians Tuesday, officials said, as violence escalated ahead of a planned peace summit.

President Petro Poroshenko said that rockets from a Tornado multiple launch system hit the command center in Kramatorsk, a town behind the front lines which is considered to be under firm government control.

Local officials said the strikes killed six people and wounded 21 in nearby residential areas.

Ukrainian foreign ministry official Dmytro Kuleba tweeted that the rockets were Tornados, "Russia's newest Multiple Launch Rocket System. Ukraine simply doesn't have it."

Kiev accuses Moscow of supplying and training heavily armed separatists, but Russia denies this claim.

Rebels say their weapons have been captured from Ukrainian forces, although Kiev has cited many cases of rebels deploying advanced weapons that are only available from Russian arsenals.

Kramatorsk was recaptured by government forces from rebels in June and made the regional capital of Ukrainian-controlled territory.