Islamic State militants have launched an offensive against a predominantly Kurdish city on the Syrian-Turkish frontier, a Kurdish official and an activist group said Wednesday.

The campaign's ultimate target is Ras al-Ayn, a town of some 50,000 people and home to a border crossing with Turkey, although the fighting is currently limited to the surrounding countryside.

Kurdish Democratic Union Party spokesman Nawaf Khalil described the Islamic State group's attack as "wide-scale and powerful."

The Britain-based Syrian Observatory for Human Rights said the fighting is focused in farmlands west and south of Ras al-Ayn. Overnight, Islamic State militants captured the village of Tal Ghanzeer, about 18 miles west of Ras al-Ayn, Observatory director Rami Abdurrahman said.

"There are more than 1,000 ISIS fighters taking part in the attack. It's a large number," he added, using an alternative name for the Islamic State group.

The IS offensive carries echoes of the militant group's ultimately failed attack on the predominantly Kurdish border town of Kobani. Kurdish fighters backed by airstrikes from the U.S.-led coalition against IS repelled that assault in January after four months of heavy fighting that left Kobani in ruins.