Ukrainian government forces reoccupied the port city of Mariupol yesterday after heavy fighting with anti-Kiev fighters.

Kiev’s Interior Ministry said its troops stormed rebel-held buildings after they were surrounded and the rebels given 10 minutes to surrender.

At least five separatists and two government soldiers were killed before the rebels retreated.

Kiev forces also regained control of a 75-mile stretch of the border with Russia.

New President Petro Poroshenko has stepped up military operations against the opposition since his election on May 25, even as he loudly proclaims his intention to bring peace to the riven country.

Kiev Interior Minister Arsen Avakov said that national guard and Interior-Ministry units took part in the battle for Mariupol alongside special forces.

The national guard was reformed after the takeover of the government by rightwingers and its Dnepr and Azov volunteer units are believed to be heavily penetrated by fascist Right Sector fighters.

Mr Avakov said government forces had raised the national flag over Mariupol’s council building by mid-morning.

Mariupol lies on major roads from the south-eastern border of Ukraine and on the Sea of Azov in the south of Donetsk region.

Elsewhere in the region a bomb went off outside an administration building in Donetsk itself.

The building is being used as the headquarters for the Donetsk People’s Republic and the bomb targeted a minibus used by one of the group’s leaders, Denis Pushilin.

Mr Pushilin was not in the vehicle at the time but separatist fighters said that two people had died and two others were injured.

They alleged the blast had been the work of Kiev’s special forces.

Meanwhile Russia was lobbying intensively at the United Nations to advance a security council resolution it introduced on Thursday that strongly urged an immediate end to all violence and the launching of a national dialogue involving all political forces and regions.

The draft resolution calls on all parties to immediately implement a “road map” to peace put forward by the Organisation for Security and Co-operation in Europe on May 12.