Explosions destroying three bridges on roads leading into the eastern Ukrainian city of Donetsk Monday may be a pro-Russian rebel attempt to hang on to one of the last major cities in their control.
The rebels mounted new barricades on the streets of Donetsk Monday, preparing to make a stand in the city after losing the embattled town of Slovyansk in the worst defeat of their three-month uprising.
Over the weekend, the Ukrainian Army drove the insurgents out of Slovyansk -- and other towns previously occupied by rebel forces -- and many fled to Donetsk, where they had previously declared independence as the Donetsk People's Republic.
The Kiev government has said it will act quickly to seize more territory from the insurgents after reclaiming Slovyansk, in what President Petro Poroshenko called a turning point in the conflict.
It was not exactly clear who blew up the highway and train bridges, but their destruction would most benefit the rebels. Bursts of gunfire were heard from the center of Donetsk, where residents said they were now living in fear of a potential battle between government forces and the separatist gunmen, Reuters reported.
Fighting between Ukrainian forces and pro-Russia separatists has 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 highway out of Donetsk, an 11-wagon cargo train was perched perilously Monday on the collapsed bridge. The road leads toward Slovyansk, a former insurgent stronghold that was recaptured Saturday by Ukrainian troops. Downing the bridge also damaged the rail line.
Anatoly Krasov, who was driving along the road Monday, said he saw an explosion before the bridge collapsed with a large cargo train on it. He said a group of men dressed in the camouflage uniforms often worn by the rebels then got into their cars and drove back toward Donetsk.
Two other bridges on roads leading from Slovyansk to Donetsk were also destroyed Monday 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. They also face little internal resistance from police forces or government officials in the city, who have done nothing in recent months to hinder their free movement around Donetsk.
Pavel Gubarev, the region's self-described governor, had promised "real partisan war around the whole perimeter of Donetsk" before thousands of supporters at a rally Sunday.
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 a rebel attempt to take control of Donetsk Airport in May, a battle that killed dozens of rebel fighters. Many residents have fled the city and the streets are often deserted but for the rebels.
Experts say that capturing Donetsk -- a city of 1 million people -- would be much more difficult than retaking Slovyansk, a city ten times smaller, and it could require the type of street-to-street urban warfare that would favor the rebels, not government troops.
On a trip to Bulgaria, Russian Foreign Minister Sergey Lavrov pressed again for a new cease-fire in Ukraine. He also condemned the OSCE for its "unrealistic demand" that the talks take place in Kiev, the capital, rather than in Donetsk.
Ukraine and the West have accused Russia of fomenting the insurgency by sending troops and weapons, including tanks and rocket launchers, something Moscow denies. Putin has so far resisted demands at home and by the rebels to come to their aid, wary of having more Western sanctions slapped on Russia.
On Monday, Russia's Foreign Ministry made its first statement about Slovyansk since the city fell. It tiptoed around the rebels' defeat, only mentioning Slovyansk as part of a long list of civilian casualties.
Russia also urged the European Union to put new pressure on Ukraine, which it accused of waging a "massive military operation which has resulted in the deaths of peaceful people."
Ukraine Defense Minister Valeriy Heletey told reporters that government forces had destroyed a large column of armored vehicles and killed dozens of rebels as they fled Slovyansk Saturday. He vowed that the army would "continue the active phase until the moment when on the territory of Donetsk and Luhansk region there is not a single terrorist left."
The Wall Street Journal reported that rebels had abandoned the town of Kramatorsk, just south of Slovyansk, while the BBC reported that the cities of Artyomivsk and Druzhkivka had also been retaken by Ukrainian forces in another sign of the army's increased traction in the east.
"I'm very disappointed," Fedor Berezin, rebel deputy defense minister, told the Journal when asked for his reaction to Moscow's lack of aid. "That means it will be a long and bloody war until we all die valiantly on the barricades."
Pavel Gubarev, the self-described governor of the Donetsk People's Republic, told the crowd that the insurgents could easily die in Donetsk if Russia did not do more to help them. Gubarev said rebels were forced to flee Slovyansk because several commanders had betrayed Girkin and left his forces there vulnerable to attack.
"We will begin a real partisan war around the whole perimeter of Donetsk," Gubarev promised in his address. "We will drown these wretches in blood."
The Associated Press contributed to this report.