The Associated Press

NOVOBAKHMUTIVKA, Ukraine – Three bridges over roads leading into the eastern Ukrainian city of Donetsk were destroyed Monday by explosions, blocking key access routes to the rebel-held city.

An Associated Press reporter saw one collapsed bridge in the village of Novobakhmutivka, where a rail line crosses over a highway leading out of Donetsk. The road leads toward Slovyansk, a former stronghold of the pro-Russian insurgents that was retaken by Ukrainian troops on Saturday after a night of intense fighting.

Anatoly Krasov, who was driving along the road on Monday, said he saw an explosion before the bridge collapsed with a large cargo train on it. He said he saw a group of men, wearing the camouflage uniforms often worn by the rebels, get in their cars and drive away from the bridge in the direction of Donetsk.

Two other bridges on roads leading from Slovyansk to Donetsk were also destroyed on Monday in the villages of Zakitne and Seleznevka, the Road Transportation Agency of Donetsk Region announced in a statement.

Rebel fighters from Slovyansk and other towns taken over by the Ukrainian army regrouped Sunday in Donetsk, a city of 1 million and the capital of a region where pro-Russian separatists have declared independence as the Donetsk People’s Republic.

The bridges’ destruction may be an attempt by the rebels to buy time and slow down any assault by Ukrainian forces on the city. Pavel Gubarev, the self-described governor of the Donetsk People’s Republic, has promised “real partisan war around the whole perimeter of Donetsk.”

The insurgents control the regional administration building and checkpoints on the city outskirts, and they were cheered by thousands of supporters waving flags from Russia and the self-proclaimed independent Donetsk People’s Republic on Sunday. They also face little internal resistance from police forces or government officials, who have done nothing in recent months to hinder their free movement around the city.

But it is unclear whether they will be able to put up major resistance in the face of a Ukrainian attack. Ukrainian forces demonstrated their superior firepower in repelling a rebel attempt to take control of Donetsk’s airport in late May, a battle that left dozens of rebel fighters dead.