The town of Al-Zakat and the Al-Arba'een village in Hama province came under regime control on Wednesday morning, the Syrian Observatory for Human Rights said.

It said the clashes overnight killed 10 regime loyalists and 18 opposition fighters, including 13 militants.

The push has also seen regime loyalists reach the edges of Kafr Zita and Al-Latamneh - respectively, a major town and a village - held by the opposition in northern Hama, according to the Observatory.

Hayat Tahrir al-Sham (HTS), a militant group led by Syria's former Al-Qaeda affiliate, has since January controlled Northern Hama as well as all of Idlib and adjacent parts of Aleppo and Latakia governorates.

A truce that started on Friday was supposed to protect three million people living in the region after three months of deadly bombardment by the regime and its ally Russia.

But HTS on Saturday refused to comply with a key condition to that truce, declaring it would never withdraw from a planned buffer zone around the area.

On Monday, the government declared the truce over, accusing its opponents of attacking civilian areas and bombarding an air base of its ally Russia.

Moscow and Damascus have since resumed air strikes.

"The regime leveraged the ceasefire to send reinforcements to Northern Hama," said Rami Abdul Rahman, the head of the Britain-based monitor.

A Turkish-Russian deal struck in September last year was supposed to avert a massive government offensive on the Idlib region.

But that deal was never fully implemented as militants refused to withdraw from the planned demilitarised cordon.

Instead, heightened attacks by the regime and Russia have killed more than 800 civilians since the end of April, the Observatory says.

It has also pushed 400,000 people from their homes, according to the UN.

Syria's conflict has killed more than 370,000 people and driven millions from their homes since it started with the brutal repression of anti-government protests in 2011.