The Ukrainian military scored a major victory in eastern Ukraine on Saturday, driving separatists from their long-held base in Slovyansk.

Rebels fled the city in about 20 military transport vehicles and buses, according to Reuters. They’ve occupied the city since April 6.

Ukrainian President Petro Poroshenko ordered the Ukrainian flag to be flown at government buildings in the city, where many were replaced with Russian flags during the uprising. He said that locals were turning in weapons left by rebels.

According to local sources, the rebels were outnumbered 50 to one.

Alex Borodai, the leader of the self-proclaimed Donetsk People’s Republic told Russian media that “given the disproportionate numerical superiority of the enemy troops, units of the armed forces of the Donetsk People's Republic were forced to leave their previous positions on the northern sector of the front.”

Rebels reportedly went to nearby Kramatorsk and Artemovsk at one point, but were also seen fleeing Kramatorsk.

On Friday, Poroshenko agreed to meet with separatist leaders to negotiate an end to hostilities, but it isn’t clear if that plan will be honored. Ukrainian, German, French and Russian foreign ministers met in Berlin earlier this week to discuss the situation. Saturday was set as the deadline for the meeting, but there has been no confirmation of the talks taking place.

On Monday, Poroshenko canceled a 10-day unilateral ceasefire. The Ukrainian military has since engaged in around 100 operations against armed eastern separatists in which 18 Ukrainian servicemen were killed. There are no estimates of how many rebels or civilians have been killed since the ceasefire ended.

Poroshenko vowed to "liberate our land" in a speech on Monday after announcing the end of the ceasefire. Poroshenko accused separatists of breaking the unilateral ceasefire. Russian Foreign Minister Sergey Lavrov said it was unrealistic to believe a unilateral ceasefire would be respected by separatists.

Slovyansk is about 70 miles north of the Oblast capital, Donetsk and is home to 120,000 people, but many fled during the last three months of unrest.

Russia halted the transfer of Ukrainian military hardware siezed during the Crimea occupation in response to the continuing Ukrainian campaign.