KIEV, Ukraine — Separatist rebels retreated Monday from positions in eastern Ukraine, apparently blowing up bridges, and began building barricades in the two largest cities, Donetsk and Luhansk, in anticipation of a final stand against advancing government troops.
While separatist leaders have complained bitterly about being sold out by their allies in Moscow, Ukrainian officials said Monday that they had succeeded in sealing the previously porous border with Russia, stopping the influx of new weapons and fighters.
The action Monday came after a series of surprising successes by Ukraine’s underequipped and underfunded military, which in recent days has driven the rebels from some strongholds that were seized early in the three-month rebellion. It has accomplished this without encountering strong resistance or a reaction from Moscow.
Ukraine’s president, Petro Poroshenko, called off a cease-fire last week and vowed to defeat the rebels on the battlefield. But that has raised the prospect of protracted and bloody urban warfare with significant civilian casualties.
Russia’s president, Vladimir Putin, who warned last week that he would not stand by while the safety of Russians was endangered, did not comment on the deteriorating situation. That was left to the foreign minister, Sergey Lavrov, who complained about damage to civilian areas but mentioned nothing about possible military action. The Kremlin appears to have taken that option off the table, in favor of a negotiated settlement that might install close allies of Russia as the governors of Donetsk and Luhansk.
“A quick end to the bloodshed is in our common interest,’’ Lavrov said at a news conference in Sofia, Bulgaria. “We believe that there can be no excuses, pretexts for postponing the immediate end of the shooting, as a result of which more peaceful civilians suffer, the outflow of refugees multiplies and civilian infrastructure is destroyed.’’
In an apparent bid to slow the oncoming troops, the pro-Russian insurgents blew up two bridges on the road to Donetsk from Slovyansk and Kramatorsk, two long-occupied provincial cities where rebels were ousted over the weekend after a fierce bombardment.
At the same time, Ukrainian officials said their troops were setting up blockades to isolate separatists in the cities. “The points of access to these cities are being blocked so that militants are not delivered weapons or manpower or other resources,’’ Andriy Lysenko, a spokesman for Ukraine’s National Security and Defense Council, said at a briefing in Kiev.
Although the military has made substantial gains in recent days, analysts warned that battles in the big cities could represent an entirely different and awful chapter, involving dangerous urban warfare and potentially high numbers of civilian casualties. Rebel forces have appeared to make a strategic calculation to abandon other positions and fall back into the urban centers, said Oleksiy Melnyk, a security analyst at the Razumkov Center, a policy research institute in Kiev.
“It’s in their advantage to get into the big cities, because the options of the government forces will be even more limited,’’ Melnyk said. “They can’t use artillery, aircraft.’’
Donetsk is a city of 1 million, Luhansk of more than 400,000, although large numbers of civilians have been fleeing, terrified of being caught in the hostilities.
Late Sunday, Rinat Akhmetov, Ukraine’s richest man, issued a plea that his home city be spared destruction. “Donetsk must not be bombed,’’ Akhmetov said. “Cities, towns and infrastructure must not be destroyed.’’
Such destruction, however, was underway. In addition to the road bridges, in the villages of Zakitne and Seleznevka, rebels destroyed a railroad bridge in the village of Novobakhmutivka, leaving a freight train dangling. In all, seven bridges were destroyed, Ukrainian officials said.
Calling the situation in eastern Ukraine worse than in Belgrade ahead of the civil war that broke apart Yugoslavia, Lavrov urged the resumption of peace talks with the inclusion of representatives of the militants from the east.
Negotiations have faltered since Poroshenko called off the cease-fire, saying it was playing into the rebels’ hands. An abridged session in Kiev on Sunday involved representatives of Ukraine, Russia and the Organization for Security and Cooperation in Europe, but Lavrov described it as pointless without the participation of militants, who he noted could not travel to the capital “for obvious reasons.’’
Echoing Lavrov, the German government on Monday issued an urgent plea, calling for a rapid, unconditional and mutual cessation of hostilities, and said it was urgent to organize talks that included the separatists. However, in a television interview, the deputy chief of staff of Poroshenko’s administration, Valeriy Chaly, said Ukraine would follow its own course.
“How to solve the situation in the country — it is our sovereign right,’’ Chaly said.
As all sides braced for fighting in the main cities, in Slovyansk it was clear that even if government forces prevail, the city faces a long recovery from the physical and emotional damage of what has effectively become a vicious civil war.
On Monday afternoon in Slovyansk, Ukraine’s interior minister, Arsen Avakov, stood under a statue of Lenin, promising to bring the “terrorists’’ to justice and restore basic services to the city by the end of the day.
Residents greeted him with questions about reconstruction and compensation for damages as a light mist coated the central square. Some shed tears at the mere mention of running water.
“What kind of future is there for Ukraine?’’ one elderly woman in a blue plastic poncho asked the minister.
“A beautiful one,’’ Avakov said, flashing a smile.
But beauty was nowhere to be found in Slovyansk, where broken glass, severed electrical cables and a wasteland of unexploded mortar shells define the landscape. Control came at the expense of untold destruction.
Outside a gold-domed church on the northern edge of the square, Ukrainian soldiers distributed water from the back of a truck. While thirsty residents accepted the aid, their attitudes toward the new armed arrivals were decidedly mixed.
Sveta Zinovyeva, 17, spent the end of her school year holed up in a basement with her family. She said she had read romance novels to distract from the “horrible fear.’’
“We can’t forget this,’’ she said. “What did we do to them? What did we do?’’