Anti-Kiev separatists in eastern Ukraine blew up three bridges on key roads leading into the regional capital Donetsk yesterday.

The actions were designed to slow down any ground offensive by government forces on the rebel-held stronghold.

Separatist fighters driven out of Sloviansk and other eastern towns by the Ukrainian army over the weekend have regrouped in Donetsk, where pro-Russia rebels have declared independence as the Donetsk People’s Republic. 

Pavel Gubarev, the putative governor, promised “real partisan war around the whole perimeter of Donetsk” when he addressed thousands of supporters at a rally in the city on Sunday.

Battles between government forces and pro-Russia separatists have left more than 400 people dead and thousands homeless since they began in early April.

In the village of Novobakhmutivka, where a rail line crosses over a main road out of Donetsk, an 11-wagon cargo train was perched perilously yesterday on the collapsed bridge. 

The road leads toward Sloviansk, a former rebel stronghold that was recaptured Saturday by Kiev’s troops. 

Downing the bridge also damaged the rail line.

Two other bridges on roads leading from Sloviansk to Donetsk were destroyed in the villages of Zakitne and Seleznevka, the Road Transportation Agency of Donetsk Region said.

The insurgents control the regional administration building in Donetsk and checkpoints on the city’s outskirts. 

But it is unclear whether they will be able to put up major resistance in the face of a Ukrainian military attack. 

Ukrainian forces demonstrated their superior firepower in repelling an attempt to take control of Donetsk airport in May, when dozens of rebel fighters were killed. 

On a trip to Bulgaria, Russian Foreign Minister Sergei Lavrov pressed again yesterday for a new ceasefire in Ukraine. 

He also condemned the Organisation for Security and Co-operation in Europe for its “unrealistic demand” that talks take place in Kiev rather than in Donetsk.

Russian President Putin has so far resisted demands at home and by rebels to come to their aid.

Russia’s Foreign Ministry urged the European Union yesterday to put new pressure on the Kiev government, which it accused of waging a “massive military operation which has resulted in the deaths of peaceful people.”