BEIRUT, Lebanon — Activists say Islamic State fighters have launched a surprise attack on a Syrian border town recently taken over by U.S.-backed Kurdish forces.

Kurdish activist Mustafa Bali and Rami Abdurrahman of the Syrian Observatory for Human Rights, a monitoring group, say IS fighters attacked Tal Abyad on the Turkish border on Tuesday, entering from the east.

Bali says fierce gunbattles raged for up to three hours between the two sides before the IS fighters took shelter in an empty school building.

Kurdish forces drove IS fighters out of Tal Abyad earlier this month, depriving the extremist group of a key point for bringing supplies and foreign fighters into Syria.

Rudaw