Rebel commanders say offensive has not yet started despite escalation that killed at least six civilians.

Antakya, Turkey – Syrian government forces backed by their Russian allies have stepped up their bombardment of rebel-held territories in northwest Syria, killing at least six civilians, according to local activists.

The air raids and shelling on Saturday came a day after Russia rejected a Turkish call for a ceasefire in Syria’s Idlib province, where a major government assault aimed at recapturing the last rebel stronghold in the country is seemingly imminent.

The attacks targeted areas in southern Idlib province and in the north of neighbouring Hama province, in what is seen as the biggest escalation over the past week.

One hospital in the village of Hass in southern Idlib was destroyed by a barrel bomb dropped from a helicopter.

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Local activists told Al Jazeera that six civilians died in the bombardment, including one child.

According to Abd al-Kareem al-Rahmoun, a representative of the White Helmets, a volunteer rescue group operating in rebel-held parts of Syria, the town of Qalaat al-Madiq in northern Hama province was targeted with more than 150 shells.

The shelling killed two men and wounded five others, including two children.

At least 26 people in rebel-held areas have been killed since the beginning of the month, the White Helmets said.

Rebel factions in northern Hama province responded to Saturday’s attacks with rocket fire and shelling of areas under government control, including the city of Salhab further west. According to the UK-based Syrian Observatory for Human Rights (SOHR), there were no reported casualties.

On Friday, rebel shelling killed 10 people, including five children in the Christian-majority town of Maharda in western Hama province, SOHR reported.

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Mohamad Haj Ali, commander of the First Coastal Division, which is part of the moderate opposition formation al-Jabha al-Wataniya lil-Tahrir (NLF), told Al Jazeera that despite the escalation, the battle for Idlib has not started yet.

“[The offensive was delayed] because of Turkish pressure on the Russians. We still hope for a diplomatic solution,” he said, adding, however, that he expects the offensive to be launched in the coming weeks.

If this happens, its first stage will target northern Latakia province and the area around the town of Jisr al-Shaghour in southern Idlib, he said.

In a separate development, clashes erupted between Syrian troops and Kurdish security forces known as Asayesh in the Kurdish-majority city of Qamishli in northern Hasakah province.

At least 13 members of the government forces were killed and seven Asayesh fighters, according to SOHR.

Although Qamishli is fully controlled by Kurdish forces, Damascus has retained control of a military base in its outskirts.

What next after Tehran summit?

In a summit on Friday in the Iranian capital, Turkey – which backs certain rebel groups in Idlib – and Assad allies Russia and Iran failed to reach an agreement on the fate of the province, which is home to about three million people, half of whom are internally displaced.

Turkish President Recep Tayyip Erdogan’s proposal for a cessation of hostilities was rejected by his Russian counterpart, Vladimir Putin.

Naji Abu Hadhifa, a spokesperson for the NFL, told Al Jazeera that nothing has changed after the Tehran summit, which confirmed the armed opposition’s low expectations.

According to Hadhifa, the intensified bombardment of southern Idlib and northern Hama provinces is aimed at frightening the civilian population.

He added, though, that the armed opposition has stepped up preparations to deal with a large-scale government offensive, and even a feared chemical attack.

Hadhifa also accused Russia of trying to sow divisions within the opposition by “lying” that there are some factions who want reconciliation and are seeking to establish contact with the Syrian government or Moscow.

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Earlier on Saturday, Turkish Foreign Minister Mevlut Cavusoglu also downplayed the current escalation and said that Turkey is currently working hard to de-escalate the situation.

“The terrorist groups in Idlib were brought there by those who are now attacking them – from Aleppo, Homs, the south – through corridors. We warned them that this would be a problem in the future … and now they use it as an excuse,” said Cavusoglu, referring to the humanitarian corridors Russia established after reconciliation deals with rebel factions that allowed them to relocate to Idlib as advancing government forces moved into opposition-held territory.

Russia has justified its intention to launch an offensive on Idlib by citing the presence of “terrorists” in the province.

Cavusoglu also said that if fighting escalates, some two million people would head to the Turkish border, which would affect both Turkey and Europe.