A Kurdish militia pressed an offensive against the Islamic State group in northeast Syria on Wednesday, cutting one of its supply lines from Iraq, as fears mounted for dozens of Christians abducted by the hardline group.

At least 90 Assyrian Christians were seized from villages in Hasaka province in a mass abduction coinciding with the offensive in the same region by Kurdish forces backed by U.S.-led airstrikes, according to the Syrian Observatory for Human Rights, which tracks the conflict.

The Syriac National Council of Syria put the figure as high as 150. Hundreds more Christians have fled to the two main cities in Hasaka province, according to the Syriac council and the Observatory.