BEIRUT >> U.S.-backed Syrian fighters resumed their offensive on the last area held by the Islamic State group in eastern Syria today after days of calm that saw thousands of civilians leave the area.

Mustafa Bali, a spokesman for the Kurdish-led Syrian Democratic Forces, tweeted that operations began after the deadline for IS gunmen to surrender expired.

Around sunset, sniper fire was seen coming from IS positions as the SDF pounded the area held by the extremists. An SDF commander who identified himself as Bilal said today’s fighting “was the heaviest clashes he’d seen since then.”

The fighting came a day after an SDF official said they could soon resume the offensive against IS, adding that the battle could last three days. SDF official Aras Orkesh said on Saturday that about 2,500 fighters are ready for the battle in and around the eastern village of Baghouz, where IS fighters still have a presence.

Under the cover of heavy coalition bombing on March 1-2, SDF forces advanced on the besieged tent encampment, leaving a corridor for residents to leave. Following that operation, thousands of residents and many fighters evacuated Baghouz over the next four days. But since Friday, only a small group has come out, raising speculation that a renewed military offensive is about to begin.

Bali, the SDF spokesman, tweeted today that the decision to resume the offensive came after thousands of civilians left Baghouz, which is the last village held by IS.

“Our forces are ready now to start and finish what is left in ISIS’s hand” Bali added.

A U.S. senior defense official said in Washington on Friday that it would not be a surprise, based on current conditions, if it took another couple of weeks to finish “mopping up” the IS enclave.

The official who could not be identified by name under Pentagon ground rules, said that nearly all of the 20,000, including women and children, are seen as IS followers or adherents.

The area on the east bank of the Euphrates River in the province of Deir el-Zour that borders Iraq has been under attack by the SDF since September. After capturing the surrounding towns and villages over the past six months, the SDF in recent weeks advanced on Baghouz from three sides, besieging it.

The capture of Baghouz would be a milestone in the devastating four-year campaign to defeat the group’s so-called “caliphate” that once covered a vast territory straddling both Syria and Iraq. The fight against IS has taken place amid Syria’s nearly 8-year-old civil war.

In southern Syria, dozens of people demonstrated today in the city of Daraa to protest the construction of a statue of late Syrian President Hafez Assad, days before the country marks the eighth anniversary of the country’s crisis, Syrian opposition activists said.

Daraa is the city where the Arab Spring-inspired uprising began with peaceful protests in March 2011 but escalated into an armed rebellion that has killed more than 400,000 people. Last year, Syrian government forces captured all parts of southern Syria, including parts of Daraa city where tensions still exist.

The late Assad is the father of President Bashar Assad whose forces have made major gains over the past few years in the war with backing from his strong allies, Russia and Iran.

The Britain-based Syrian Observatory for Human Rights, a war monitor, said the protest occurred in Daraa’s center with protesters chanting “Long live Syria” and “Down with Bashar Assad.”

The Observatory’s chief Rami Abdurrahman said security forces did not interfere in the protest.

Other opposition activist collectives, including Sham Network, also reported the protest.