Regime air strikes on Saturday killed 12 civilians in northwest Syria, where ramped up attacks by Damascus and its ally Russia have claimed the lives of hundreds since late April.

Idlib and parts of the neighbouring provinces of Aleppo, Hama and Latakia are under the control of Hayat Tahrir al-Sham, a militant group led by Syria's former Al Qaeda affiliate.

The region is supposed to be protected from a massive government offensive by a September buffer zone deal, but it has come under increasing bombardment by the regime and its Russian ally over the past three months.

On Saturday, two children were among 11 civilians killed in air raids on the Idlib town of Ariha, said the Syrian Observatory for Human Rights.

The attack wounded 28 others, said the Britain-based monitor.

Two residential buildings in Ariha were hit by raids, in the second such attack on the town this week, said Observatory head Rami Abdul Rahman.

Regime air strikes killed 10 civilians in Ariha on Wednesday, according to the Observatory.

Bombardment by government forces on other parts of the Idlib region killed another civilian on Saturday and wounded 15 others, the monitor said.

Air strikes by the Syrian regime and its ally Russia on the Idlib region have claimed more than 740 lives since late April, according to the Observatory.

The UN says more than 400,000 people have been displaced.

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The UN Office for the Coordination of Humanitarian Affairs (OCHA) has documented 39 attacks against health facilities or medical workers in the area in three months.

At least 50 schools have been damaged by air strikes and shelling over the same period, it said.

“These are civilian objects, and it seems highly unlikely, given the persistent pattern of such attacks, that they are all being hit by accident,” UN rights chief Michelle Bachelet said on Friday.

Suicide bomber kills 6 regime soldiers

Meanwhile, a suicide bomber killed six soldiers on Saturday in the southern province of Daraa, in a rare deadly attack against the cradle of the uprising that sparked Syria's war, a monitor said.

The bomber, who was riding a motorcycle, blew himself up at a military checkpoint killing the six soldiers and wounding several other people, the Britain-based Syrian Observatory for Human Rights said.

Syria's state news agency SANA also reported a suicide bombing but said it happened during an “army raid” that targeted “terrorists”, a term used by authorities to describe rebels and militants.

SANA said several soldiers were wounded when “a terrorist detonated an explosive belt during an army raid”.

It was not immediately clear who was behind the blast, but pro-regime forces in Daraa province face explosions and gunfire on a near daily basis, although they are usually not deadly.

Earlier this month, an six soldiers were killed in an explosion that targeted an army convoy near Yadud village, some seven kilometres (four miles) outside the provincial capital of Daraa city, according to the Observatory.

Russia-backed government forces last summer retook the province, following a deadly bombardment campaign and surrender deals that saw part of the population board buses to a northern opposition holdout.

Government institutions have since returned, but army forces have not deployed in all of the province.

And local anger has grown after hundreds were detained despite the so-called “reconciliation deals”, and many others forcibly conscripted into President Bashar al-Assad's army.

In March, dozens of people took part in a protest after a statue of the president's late father, Hafez al-Assad, was erected in Daraa to replace one destroyed by protesters at the onset of the 2011 uprising.

Syria's eight-year conflict, which evolved from a brutal crackdown on anti-government protests into a full blown civil war involving regional and international players, has killed more than 370,000 people.