A UN commission on Wednesday said rebel groups in Syria's Idlib province should leave urban areas to protect civilians from a looming government assault.

"Most of those terrorist groups and other armed groups, they are in the cities. Perhaps one wonderful scenario is: leave the cities," said UN Commission of Inquiry on Syria chief Paulo Pinheiro.

Hany Magally, a fellow panel member, said: "Shouldn't the armed groups move out and spare the civilian population?"

The proposal comes after the United Nations' peace envoy for Syria, Staffan de Mistura, last week suggested a deadline be set for fighters in Idlib to pull back from its cities.

UN agencies and relief organisations have warned repeatedly that any major assault on the province of Idlib, which borders Turkey, could spark one of the worst humanitarian disasters of Syria's seven-year war.

UN chief Antonio Guterres warned on Tuesday that a full-scale battle in Idlib "would unleash a humanitarian nightmare unlike any seen in the blood-soaked Syrian conflict".

Idlib and adjacent areas are largely controlled by Hayat Tahrir al-Sham (HTS), an alliance led by al-Qaeda's former Syrian affiliate, as well as rival rebels. HTS controls the provincial capital, Idlib city.

The northwestern region has seen its population almost double with the arrival of Syrians displaced from other parts of the country, many of whom already depend on aid.

"All the other disasters would be minor events compared to what can happen in Idlib," Pinheiro said.

On Wednesday, intermittent artillery fire hit a number of southern districts within Idlib province and neighbouring rebel-held areas of Hama province, a Britain-based monitor said.

But for the second day in a row there were no air raids, after deadly strikes and barrel bombing over the weekend, said the Syrian Observatory for Human Rights.

Last Friday, Turkey, Russia and Iran failed to reach an agreement to avoid an assault on Idlib.

The head of the Istanbul-based opposition organisation Syrian National Coalition (SNC), Abdulrahman Mustafa, told Middle East Eye last week that rebel forces would not withdraw from Idlib in case of a government assault.

He said rebel groups in Idlib were trying to entice members of HTS to leave the organisation.

Syrian opposition says it will resist assault on Idlib province Read More »

“We are trying to have all the groups in the HTS to shift to the National Front for Liberation (NFL) and dissolve HTS. We will see what will happen next," he said. The NFL is an umbrella group of rebel forces backed by Turkey.

Three Turkish security and government officials told Reuters on Wednesday that troops, armoured vehicles and equipment had been sent to the Syrian border. A senior security source said the army has reinforced 12 Turkish military posts inside Idlib itself.

"We have a military presence there and if that military presence is damaged or attacked in any way, it would be considered an attack on Turkey and would therefore receive the necessary retaliation," the source said.

The observation posts were set up in the Idlib region last year under an accord with Russia and Iran designating Idlib and parts of neighbouring provinces a "de-escalation zone".