Activists say Islamic State militants are shelling a beleaguered Kurdish town in northern Syria on the Turkish border.

The Britain-based Syrian Observatory for Human Rights says the extremists fired at least 10 rockets Sunday on the town of Kobani, also known as Ayn Arab. The militants are also firing tank shells and mortars as they try to break the Kurds' hold on the town.

The Observatory says heavy clashes overnight, as well as U.S.-led coalition airstrikes on Islamic State positions around Kobani, killed at least 16 militants. At least 11 Kurdish militiamen were also killed the in the fighting.

From the Turkish side of the border, the heavy thud of shelling could be heard Sunday from Kobani, and pillars of smoke billowed over the town.