Government air raids on northwest Syria killed at least 11 people overnight, mostly civilians, a monitoring group said Monday, while the military said its forces made advances in Aleppo province.
"Government warplanes carried out air strikes after midnight on several areas in the town of Ariha" in Idlib province, said the Syrian Observatory for Human Rights' head Rami Abdel Rahman.
"The preliminary toll is 11 killed, including at least seven civilians," three of them children, he said.
Others were still missing and rescue teams were searching for anyone trapped under the rubble, Abdel Rahman added.
Leith Fares, a rescue worker in Ariha, told AFP his team had pulled at least 20 wounded people out of the rubble.
"We've been working since 3:00 am (0100 GMT) to rescue victims still under the rubble of two four-storey buildings that totally collapsed on the residents inside," he said.
"We're still looking for two families, estimated at eight to 10 members each, that are still trapped," Fares said.
The deaths come two days after 10 civilians were killed in government air strikes on Ariha, held since spring 2015 by an anti-regime coalition dominated by jihadists.
Idlib province has been battered by heavy air strikes in recent weeks, with intensifying bombing raids by regime warplanes in particular, according to the Observatory.
It has also been rocked by infighting between rebel and jihadist factions, including Al-Qaeda's former Syrian affiliate, Fateh al-Sham Front.
- Regime advance in Aleppo -
Syria's conflict began in March 2011 with protests against President Bashar al-Assad's rule but has since spiralled into a multi-front civil war pitting government forces, rebels, jihadists and Kurds against each other.
Troops loyal to Assad scored their biggest victory yet in late December when they secured full control of Syria's second city Aleppo.
In recent weeks, they have also steadily advanced on several fronts in the province of the same name, including against the Islamic State jihadist group.
A Syrian military source told AFP on Monday that the army had "seized 18 towns and villages, including the town of Taduf and a number of strategic hilltops in eastern Aleppo province, totalling about 600 square kilometres (230 sq miles)."
Taduf had been held by IS jihadists and lies near Al-Bab, a key town where rebel fighters, backed by Turkish soldiers, artillery, and air power, defeated IS last week.
IS on Monday also withdrew from nearly two dozen villages near the town of Manbij, in what the Observatory called a sign of "swift collapse" of jihadist ranks.
Manbij is held by the Syrian Democratic Forces, a US-backed alliance of Kurdish and Arab fighters.
"Regime forces moved into those 23 villages, linking up with SDF forces in the area," said Abdel Rahman.
The government's advance in the area is, according to the Observatory, part of a bid to block the Turkish-backed forces from expanding their zones of control in Aleppo province.
But regime troops are also trying to advance east to reach IS-held Khafsah, the main station pumping water into Aleppo city, Abdel Rahman said.
Residents of the northern city have been left without water for 42 days, after IS jihadists cut the supply at Khafsah -- around 90 kilometres (55 miles) away.