By Ellen Francis and Rodi Said

DEIR AL-ZOR PROVINCE, Syria (Reuters) – U.S.-backed Syrian fighters launched an operation on Friday to clear the last remaining pocket of Islamic State fighters from the besieged eastern Syrian village of Baghouz after weeks of delays caused by the evacuation of thousands of civilians.

The Syrian Democratic Forces (SDF) moved on the enclave, a tiny area on the eastern bank of the Euphrates River, at 6 p.m. (1600 GMT) after the last batch of civilians were removed, said Mustafa Bali, the head of the SDF media office.

“Nothing remains in Baghouz except for terrorists. The battle … will not end until the elimination of Daesh and the liberation of the village,” he told Reuters, using an Arabic acronym for Islamic State.

Bali said the initial fighting involved heavy weapons. Asked how long the battle would last, he said: “We expect a fierce and heavy battle.”

The Islamic State enclave at Baghouz, a tiny pocket on the eastern bank of the Euphrates River, is the last populated territory held by the jihadists, who have been steadily driven by an array of enemies from swathes of land they once held.

Though the fall of Baghouz will mark a milestone in the campaign against Islamic State, the group continues to be seen as a security threat, using guerrilla tactics and holding some desolate territory in a remote area west of the Euphrates River.

The SDF commander-in-chief said on Thursday that his force would declare victory over the jihadists in one week.

(Additional reporting by Tom Perry in Beirut and Stephanie Nebehay in Geneva; Writing by Tom Perry/Stephen Kalin in Beirut; Editing by Kevin Liffey)