DONETSK, Ukraine — A rebel stronghold in east Ukraine has been taken by government troops, the country's president and a spokesman for the rebels said Saturday.

President Petro Poroshenko said in a statement that government troops took the city of Slovyansk, a city of about 100,000 that has been a center of the fighting between Kiev's troops and the pro-Russian insurgents, after a night of fighting.

Poroshenko commanded the armed forces to "raise the government's flag" over Slovyansk, which has been under rebel control since early April when they seized the city's administrative and police buildings.

Rebels fleeing from the city of Slovyansk vowed to regroup elsewhere and fight on.

Andriy Lysenko, spokesman for the National Security and Defense Council, said mopping-up operations were continuing.

"Slovyansk is under siege. Now an operation is going on to neutralize small groups hiding in buildings where peaceful citizens are living," Lysenko told journalists.

Andrei Purgin of the separatist Donetsk People's Republic told The Associated Press that rebels were evacuating, but claimed the army's campaign had left the city "in ruins."

Purgin claimed 150 fighters injured in Slovyansk were in Donetsk for treatment.

Alexei, a driver and local Slovyansk resident who would not give his last name for fear of reprisal, told the AP by phone that he heard bombing throughout the night. When the bombing stopped in the early morning, he left his house and saw that all the rebel checkpoints were abandoned. He said there was some damage to buildings in the center of the city, but said much of the rest of the city had been left untouched.

A rebel commander who would only give his nom de guerre as Pinochet told the AP that rebels had relocated to the nearby town of Kramatorsk, about 12 miles south of Slovyansk.

Poroshenko said Friday he was ready to conduct another round of talks between representatives from Ukraine, Russia and the rebels.