Syria Army troops and Kurdish forces, who share control of the city, had been battling since June 25 to push the terrorists group out of the city, which is the capital of Hasakeh province.

ISIS "was expelled by the army from Zuhur, the last district in which it was present in Hasakeh, and its fighters have been pushed to the southern outskirts of the city," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

He said at least 287 ISIS fighters, among them 26 minors, had been killed in the fight for Hasakeh, as well as strikes by the US-led coalition outside of the city.

ISIS has attacked Hasakeh city several times, but the June 25 assault was the group's most serious yet.

Its forces initially seized several districts in the southern part of the city, with Kurdish fighters and Syrian troops mobilizing against them.

The Observatory said ISIS had used at least 21 car bombs and several suicide bombers during the month-long fight.