U.S.-backed Syrian forces on Friday declared “total liberation” of Raqqa, the Islamic State in Iraq and Syria’s self-declared capital since 2014.

Syrian Democratic Forces (SDF) spokesman Talal Silo called the liberation a “historic victory” over ISIS. At a ceremony to celebrate the city’s recapture, Silo said ISIS suffered a “brutal” defeat.

The SDF, a U.S.-backed mix of Kurdish and Arab fighters, has spent the last four months taking back the city block by block.

Coalition Director of Operations Brig. Gen. Jonathan Braga, using an Arabic term for the terrorist group, said the SDF “fought tenaciously and with courage against an unprincipled enemy, taking great care to move the population trapped by Daesh away from the battle area and minimize civilian casualties.”

ADVERTISEMENT

The SDF on Tuesday had declared that fighting had ended in Raqqa, but about 100 ISIS fighters remained, said Army Col. Ryan Dillon, a coalition spokesman

Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE released a statement Friday congratulating the forces on the liberation, calling it a “critical milestone in the global fight against ISIS” and the beginning of a “new phase” in the country.

Tillerson cautioned however, that work is far from over.

“As we and our partners push toward the territorial defeat of ISIS, we will continue to seek to de-escalate violence across Syria,” Tillerson said. “The Coalition will continue its relentless campaign to deny ISIS safe haven anywhere in the world, and sever its ability to recruit, move foreign terrorist fighters, transfer funds, and spread false propaganda over the internet and social media.”

Tillerson added that the the U.S. and other coalition members are working to remove explosives in Raqqa left by ISIS.

Dillon told reporters Tuesday that the SDF will now look to an area known as the Middle Euphrates River Valley in Syria's Deir ez-Zour province, where fighting has already begun.

There are roughly 6,500 ISIS fighters left in Syria and Iraq.