DAMASCUS - The Syrian army has entered all areas in the town of Khan Shaykhun after the defeat of the rebel groups in that area in the countryside of Idlib province, a military source told Xinhua on Thursday.

The source said the army units entered all areas in Khan Shaykhun, a former rebel bastion that was retaken by the army on Wednesday.

The source said the military campaign that led to capturing the Khan Shaykhun had started from areas in the adjacent northern countryside of Hama province in central Syria.

"After launching the military operation from the northern countryside of Hama toward the towns of the southern countryside of Idlib, the army captured the town of Khan Shaykhun, which is considered as one of the major fortifications of the terrorist groups in Idlib," he said.

He noted that the progress enabled the army to complete the siege on key rebel-held areas in the northern countryside of Hama.

"With this progress, the army has completed the siege on the towns of Morek, al-Lataminah and Kafr Zita," he said.

The army has recently advanced to the town of Khan Shaykhun in a bid to capture it and secure the part of the main Damascus-Aleppo highway near Idlib.

Idlib and the northern countryside of Hama are included in the de-escalation zone deal that was reached between Russia and Turkey last September.

The deal, however, has largely failed despite several attempts to revive it.

The latest attempt to fix the deal came earlier this month when Turkey and Russia mediated a fresh cease-fire in Idlib, which failed quickly with the resumption of the military showdown.

Earlier in the day, the Syrian government declared opening a humanitarian corridor for civilians desirous of leaving battlefield areas in the countryside region of the provinces of Idlib and Hama, according to a foreign ministry statement.

The corridor was set up in the Souran area in the northern countryside of Hama province to enable the civilians to leave rebel-held areas in the countryside of Hama and the adjacent countryside of Idlib.

The Syrian Foreign Ministry said the measure comes in light of the Syrian government's keenness to alleviate the suffering of the civilians.

It said all the humanitarian needs of the civilians will be met such as medical help and shelters.

Several Turkey-backed rebel groups are located in the Idlib province near the Turkish border, but the most powerful group there is the Hayat Tahrir al-Sham, the umbrella group of the al-Qaida-linked Nusra Front.

For the Syrian army, securing Idlib would almost deal a definite defeat to the over eight-year-long insurgency against the administration of President Bashar al-Assad.

Idlib is also strategically important as it shares a border area with Turkey to the north. It's also close to the coastal province of Latakia, the hometown of Assad which contains a Russia-run air base repeatedly targeted by rebel drones launched from Idlib.

The capital city of Idlib also lies close to the international road linking the capital Damascus with Aleppo in northern Syria.

Around 3 million people are living in Idlib, including those evacuated from other areas during the surrenders of the rebels.