ISIS militants took back a stronghold in Syria’s northern Aleppo countryside near the border with Turkey on Monday, four days after losing it to a grouping of fighters, the Syrian Observatory for Human Rights said.

The monitoring group reported that the ultra-hardline terrorist group captured the town of al-Rai from factions fighting under the banner of the Free Syrian Army, part of months of back-and-forth fighting in northern Aleppo province.

ISIS has declared a cross-border caliphate in Syria and neighboring Iraq and is also fighting other groups caught up in Syria’s civil war.

It has made steady gains near the Azaz border crossing with Turkey since last May, but has been deterred in a number of areas in recent months by rival opposition fighters and Syrian government forces backed by Russian air strikes.