Turkish forces entered Idlib in northern Syrian Sunday following clashes with militants from Hayat Tahrir al-Sham (HTS), triggering the first signs of a battle announced two days ago by Turkish President Recep Tayyip Erdogan to re-impose security in the province. The two sides exchanged fire on Syrian grounds as Ankara deployed its forces at the border before an expected military operation to oust the Qaeda-linked militants from the province of Idlib.

Field sources at the border said that Turkish tanks offered a cover for Free Syrian Army fighters on Sunday morning while the Turkish army continued moving in the province of Reyhanli in Hatay province, near the Syrian border to help push its forces inside Idlib, part of a joint mission with Russia and Iran to monitor a ceasefire agreement in Syria’s de-escalation zones.

HTS is not part of a deal brokered by the three countries for the safe zone in the province, one of four such “de-escalation” zones across Syria. Turkish armored vehicles and troops were waiting on the border, from where smoke could be seen from the mortar fire, an AFP photographer said. Meanwhile, talks continued on Sunday among figures close from HTS in a bid to find an exit to the crisis.

Those figures want to allow the National Rescue Government led by its newly-elected president Mohammed al-Sheikh to become the civilian representative of Tahrir al-Sham and therefore shoulder the mission of negotiation concerning Idlib to keep the terrorist stain away from the HTS. Separately, a final assault on ISIS’ last line of defense in its former Syrian capital Raqqa should begin on Sunday night, a field commander for the US-backed forces operating there told Reuters.

The assault on militants in the center of the northern city will focus on surrounding the sports stadium there, said a field commander in the Syrian Democratic Forces (SDF) in western Raqqa, who gave his name as Ardal Raqqa.

On the other hand, U.S.-backed fighters in northern Syria are preparing for a final offensive on neighborhoods still held by the Islamic State group in the city of Raqqa, a spokesman for the group said Monday.

Mustafa Bali of the Kurdish-led Syrian Democratic Forces told The Associated Press that the battle is expected to last between seven to 10 days. The extremists still have hundreds of fighters in the city that was once their de facto capital.

The Kurdish-led forces launched an offensive against IS in Raqqa in early June, under the cover of airstrikes by the U.S.-led coalition. The Kurdish-led group has captured 80 percent of the city, leaving IS in control of parts of the Raqqa's center and north.

"The Syrian Democratic Forces are reinforcing positions ahead of the final attack on the city of Raqqa," Bali said by telephone on Monday, speaking from northern Syria.

He added that no time has yet been set for the attack, thereby dismissing reports in some media that the "final offensive" had started. Bali said the biggest battles are expected to take place around the Al-Aswad Football Stadium, where IS fighters used to hold detainees.

The loss of Raqqa would be another major blow to IS, which has suffered significant setbacks over the past year, including the loss in July of Mosul, Iraq's second largest city and the biggest that the extremists ever held.

The battles have been ongoing for weeks in Raqqa. SDF fighters and Syrian government forces are also marching in the eastern province of Deir el-Zour, the last stronghold for IS in eastern Syria.

Backed by Russian airstrikes, Syrian troops and their allies have been pushing along the western bank of the Euphrates River while SDF fighters are moving along the eastern bank. There have been concerns about a clash between the U.S.-backed fighters and President Bashar Assad's forces.