Ukrainian separatist rebels have pulled back to the main city of Donetsk, abandoning several strongholds in the Donetsk region to government forces.

The pro-Russian gunmen abandoned the cities of Sloviansk and Kramatorsk, as well as some smaller towns, in the north of Donetsk region.

But they have vowed to continue the fight from Donetsk city, describing the withdrawal as a tactical retreat.

Ukrainian forces launched an offensive this week after a truce broke down.

The BBC’s David Stern in Kiev says the military’s capture of Sloviansk, where the eastern insurgency began in April, is a major victory for the government.

The government said in a statement that the rebels had fled after mortar shelling from government forces.

Ukraine’s President Petro Poroshenko said the breakthrough was “the beginning of the turning point in the fight against militants”.

“This is not complete victory. But the cleansing of Sloviansk from gangs who are armed to the teeth is of huge symbolic importance,” he said in a statement.