BEIRUT — U.S.-backed, Kurdish-led fighters captured the last town held by the Islamic State group on Friday, after days of intense battles in the militants' single remaining enclave in eastern Syria, activists said.

The fall of Hajin is a blow to the extremists. The town was their main stronghold in the last pocket of land they control in eastern Syria, near the Iraqi border. ISIS still holds some villages nearby.

The Kurdish-led Syrian Democratic Forces have been fighting to take Hajin and the surrounding villages in Deir el-Zour province for over three months. In the past weeks, the offensive intensified with the arrival of reinforcements from northern Syria.

The Britain-based Syrian Observatory for Human Rights said the SDF took Hajin early in the morning, after fierce fighting under the cover of airstrikes by the U.S.-led coalition. It said some ISIS fighters withdrew to the villages and that fighting is still going in the fields outside Hajin as SDF fighters chase the extremists.

Europe-based activist Omar Abu Layla of the DeirEzzor 24 monitoring group confirmed that the town was taken, adding that some ISIS fighters are still holed up in small pockets on the edge of Hajin.

The area was home to some 15,000 people, including 2,000 ISIS gunmen who have been fighting back with counteroffensives and suicide attacks.

Over the past days, hundreds of civilians were able to flee the enclave toward areas controlled by the SDF east of the Euphrates River and government-controlled regions on the river's west bank.

ISIS was driven from nearly all the territory it once held in Syria last year in separate campaigns waged by the U.S.-backed SDF on the one hand, and the Russian-backed Syrian government on the other.