The Russian strikes on Tuesday evening and at dawn on Wednesday hit an area of the northwest where the boundaries of Hama, Idlib and Latakia provinces meet, the Syrian Observatory for Human Rights said.

The Hayat Tahrir al-Sham alliance (HTS), led by Syria's former Al-Qaeda affiliate, and its hardline allies enjoy a significant presence in the area, the Britain-based monitoring group added.

Home to some three million people, the Idlib region of the northwest is controlled by HTS and affiliated rebel groups.

A Russian-backed government offensive between December and March displaced nearly a million people in the region.

Some 840,000 of the nearly one million remain displaced, while some 120,000 have returned to their home communities since the ceasefire went into force, according to the United Nations.

The truce, which coincided with the coronavirus crisis, had put a stop to the relentless air strikes by government forces and their Russian allies that killed at least 500 civilians in four months.

The Observatory said the latest strikes were intended to push jihadists away from the key M4 highway in northern Syria, where Turkish and Russian forces often conduct joint patrols as part of the truce agreement.

They were also intended to push HTS and its allies further away from the Sahl al-Ghab area in the north of Hama province, where government and Russian forces are present, it added.

The air strikes triggered a fresh wave of displacement from Sahl al-Ghab and the Jabal al-Zawiya district of neighbouring Idlib, the Observatory added.

Nearly half of the three million people living in the Idlib region have been displaced from other parts of Syria recaptured by the government.

After holding barely a fifth of the country five years ago, Russian intervention has helped the government reclaim control of more than 70 percent of Syria.

In the northwest, HTS and its allies control around half of Idlib province and slivers of territory in the neighbouring provinces of Hama, Latakia and Aleppo.

The war in Syria has killed more than 380,000 people and displaced nearly half of the country's pre-war population since it started in 2011.

The month of May saw the lowest civilian death toll since the start of the conflict nine years ago with 71 civilians reported killed, the Observatory said on Tuesday.