Ukrainian separatists retreat to Donetsk, Luhansk

KIEV , Ukraine, July 8 (UPI) -- Pro-Russian separatists in eastern Ukraine retreated to the cities of Donetsk and Luhansk, apparently abandoning other positions as government troops advanced with little opposition.

The Ukrainian army has encountered little resistance in moving eastward and defeating strongholds of resistance, although rebels blew up bridges as they returned to fortify Donetsk and Luhansk. The army also successfully sealed the border between Ukraine and Russia, preventing the delivery of military equipment.

Ukrainian President Petro Poroshenko canceled a cease-fire to fight the rebels, and the barricades built in the two remaining cities suggest prolonged urban battles are about to begin.

"It's in their advantage to get into the big cities, because the options of the government forces will be even more limited," said Oleksiy Melnyk of Kiev's Razumkov Center, a policy research institute. "They can't use artillery, aircraft."

The army's sweep of Ukraine came without involvement from Russia, and separatist leaders are bitter about their perceived abandonment by Russia. Russian President Vladimir Putin has offered no recent comment on the Ukrainian situation, except to repeat he would protect the safety of Russians. The Kremlin appears to favor the installation of pro-Russian governors in Donetsk and Luhansk, instead of supporting combat by separatists.

"A quick end to the bloodshed is in our common interest," Russian Foreign Minister Sergey Lavrov said Monday 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."

Residents have fled Donetsk, a city of one million, and Luhansk, with a population of about 400,000, in anticipation of battles in the streets.