AMMAN (Reuters) - Russian-led air strikes killed at least 40 people on Tuesday in northwest Syria in a major army assault backed by Iranian militias to clear out rebels that has sent tens of thousands of people fleeing toward the border with Turkey, residents and rescuers said.

They said a family of eight including six children was killed in the rural village of Kfar Taal west of government-controlled Aleppo, while another nine civilians were killed in Maardabseh in the southeast of Idlib province.

“God take revenge on all tyrants. There is no one else left in my family, they are all gone,” Abu Yasser, 71, a relative of the family wiped out in Kfar Taal, said in a voice recording sent to Reuters.

At least 22 other civilians were killed in other strikes by Russian and Syrian government warplanes on rural opposition areas that have been hit hard since the Russian-led military campaign, supplemented by Iranian militias, began in December.

The aerial bombings in which Moscow has also deployed special forces on the ground to push deeper into rebel-held territory has left dozens of towns in ruins and knocked down hospitals and schools, rescuers and aid agencies say.

U.N. officials said last week a humanitarian crisis in the Idlib region of far northwestern Syria, the last significant rebel redoubt in Syria after almost nine years of civil war, had worsened with at least 350,000 civilians now on the run.

Another half a million people fled earlier bouts of fighting to the safety of camps near the border of Turkey, which backs some rebel factions in the northwest.

A ceasefire brokered between Turkey and Russia to end the latest offensive collapsed nearly 10 days ago when Moscow resumed heavy strikes on civilian areas in what residents said was a strategy of bringing the armed opposition to its knees by striking its popular base.

The latest offensive has brought President Bashar al-Assad’s military campaign closer to heavily populated central areas of Idlib, where nearly 3 million people are trapped, according to aid charities and U.N. agencies.

Moscow and Damascus deny accusations of indiscriminate bombing of civilians, saying they are fighting jihadist militants who they say have stepped up their attacks on civilians in Aleppo city in northern Syria.

Syrian state television said two women and a child were killed in a rocket attack by “terrorists” - its standard term for anti-Assad rebels - on a crowded neighborhood of Aleppo.