Smoke rises after an air strike near the Idlib province village of Kafr Ain on September 7, 2018 as the presidents of Iran, Russia and Turkey prepared for a summit in Tehran on Syria's last major rebel bastion
Russian air strikes killed five people in Syria's Idlib Friday, a monitor said, even as the brutal war's top three power brokers discussed "stabilising" the last rebel-held province.
Later in the day, shelling by hardline rebels killed 10 civilians in a neighbouring province, the Syrian Observatory for Human Rights said.
Government forces have been massing around Idlib for weeks ahead of an expected offensive on the province, which is held by jihadists led by Al-Qaeda's former Syrian affiliate and rival Turkish-backed rebels.
On Friday morning, Russian air raids targeted positions in Idlib's southwest held by the jihadist Hayat Tahrir al-Sham (HTS) alliance, as well as of the hardline Ahrar al-Sham group, the Britain-based Observatory said.
They destroyed one Ahrar al-Sham post, killing four of its fighters and wounding 14 others in the area of Hobait, it said.
An AFP stringer saw rescue workers working with their bare hands to retrieve a victim from rubble blocking the entrance of what appeared to be a cave inside a sandstone rock face.
They carried away the limp body of a man covered in pale dust, as diggers worked nearby to clear the debris.
A shepherd was also killed and four other people wounded in the bombardment, the Observatory said, although it was not immediately clear if they were fighters or civilians.
"The aim was to destroy rebel fortifications," said Observatory head Rami Abdel Rahman.
On Friday evening, hardline rebels fired shells at the town of Mahrada, which lies in the adjacent province of Hama about 15 kilometres (10 miles) south of the administrative border with Idlib.
"The bombardment was in retaliation for the earlier strikes and killed 10 civilians, including six women, three children and one man," Abdel Rahman told AFP.
- Fears of humanitarian disaster -
HTS controls more than half of Idlib province, while other rebels, including Ahrar al-Sham, hold most of the rest.
Regime troops are present in a southeastern chunk of the province, but observers say a planned offensive could target other peripheral areas of the rebel-held zone.
Russian President Vladimir Putin, who backs Syria's government, met the leaders of fellow regime ally Iran and rebel supporter Turkey to determine the fate of the northwestern zone on the Turkish border.
On Friday, Putin said that he, Iranian President Hassan Rouhani and Turkish leader Recep Tayyip Erdogan "discussed concrete measures regarding a phased stabilisation" for Idlib.
But a joint statement released after the talks gave few details.
Aid groups have warned that any military offensive in Idlib could spark one of the worst humanitarian disasters of Syria's seven-year civil war.
Almost three million people live in Idlib and adjacent rebel-held areas, half of whom have already been displaced from other parts of the country, the United Nations says.
More than 350,000 people have been killed and millions displaced since the war erupted in 2011 with the brutal repression of anti-government protests.