Ukraine's defense minister has declared that government forces will continue their offensive against pro-Russian separatists.

"Our given task is to bring peace and order to the region," said Colonel General Mykhailo Koval. He said the military action would continue "until these regions begin to live normally, until there is peace," and accused Russia of supporting the rebels.

This week 14 Ukrainian soldiers, including General Vladimir Kulchitsky, were killed when pro-Russian separatists shot down a military helicopter near the city of Slovyansk. Elsewhere, more than 100 separatists were killed in a battle for Donetsk airport, in the heaviest fighting since the crisis began.

Alexander Borodai, the leader of the Donetsk People's Republic, told the independent Russian TV channel Dozhd (Rain) that the rebels will only negotiate with Kiev if it withdrew troops from Donetsk and Luhansk.

Separatists in the Donetsk and Luhansk regions declared independence in referendums this month, which were rejected by Kiev.

In reaction to the separatist attacks, Ukraine's newly-elected President Petro Poroshenko has vowed to punish the "bandits" behind the unrest.

"These criminal acts of the enemies of the Ukrainian people will not go unpunished," he said.