At least 30 Ukrainian servicemen have been killed in a missile attack by pro-Russian rebels, according to reports.

Zoryan Shkiryak, an adviser to the interior minister, was quoted by the Interfax-Ukraina news agency as saying authorities would react swiftly to the attack.

Government troops have been mired in fighting for more than three months with a rebel force seeking secession for eastern regions of Ukraine.

Rocket attacks on army encampments and checkpoints have become an almost daily occurrence and the death toll among troops has been steadily mounting.

Government forces appeared to turn the tide last weekend when they forced rebels out of their stronghold in the city of Slovyansk.