Ukrainian officials said, however, the rebels were fighting a desperate rearguard action to hold on to Luhansk - which is their supply route into neighboring Russia - and that the flow of weapons and fighters from Russia had accelerated.
The foreign ministers of Ukraine, Russia, France and Germany held a meeting in Berlin on the crisis, with German Foreign Minister Frank-Walter Steinmeier saying afterwards they would report back to their leaders and possibly agree on Monday or Tuesday on how to continue talks.
"The aim remains to bring about a ceasefire in Ukraine and to prevent future victims," Steinmeier said.
“It was a difficult discussion but I believe and I hope that we made progress on some points,” he told reporters.
Russia denies helping the rebels and accuses Kiev, backed by the West, of triggering a humanitarian crisis through indiscriminate use of force against Russian speakers in eastern Ukraine who reject the Ukrainian government's rule, Reuters reported.
Andriy Lysenko, a Ukrainian military spokesman, said government forces fought separatists in Luhansk on Saturday and took control of the Zhovtneviy neighborhood police station.
"They raised the state flag over it," Lysenko said.
Separatist officials in Luhansk could not be reached by telephone, and a separatist spokeswoman in Donetsk, the other rebel strong-hold, said she had no information about Luhansk.