BEIRUT (AFP) - Air strikes by Damascus or its ally Moscow killed 12 civilians in a market in Syria's Idlib province, a monitor said on Wednesday (May 22), as fierce fighting raged for the Islamist-held northwestern region.

Another 18 people were wounded when the warplanes hit the extremist-held town of Maarat al-Numan around midnight on Tuesday, the Britain-based Syrian Observatory for Human Rights said.

The market was crowded with people out and about after breaking the daytime fast observed by Muslims during the holy month of Ramadan.

The strikes came as heavy clashes raged in the north of neighbouring Hama province after the extremists launched a counter-attack on Tuesday against pro-government forces in the town of Kafr Nabuda.

Fresh fighting on Wednesday took the death toll to 52 - 29 troops and militia and 23 Islamists, the Observatory said.

It said that the extremists had retaken most of the town from government forces, who recaptured it on May 8.

The Islamist-dominated Idlib region is nominally protected by a buffer zone deal, but the regime and its Russian ally have escalated their bombardment of it in recent weeks, seizing several towns on its southern flank.

An extremist alliance led by Syria's former Al-Qaeda affiliate, Hayat Tahrir al-Sham, controls a large part of Idlib province as well as adjacent slivers of Aleppo, Hama and Latakia provinces.

Russia and rebel ally Turkey inked the buffer zone deal in September to avert a government offensive on the region, which threatened humanitarian disaster for its three million residents.

President Bashar al-Assad's government has renewed its bombardment of the region since HTS took control in January.

Russia too has stepped up its air strikes in recent weeks as Turkey proved unable to secure implementation of the truce deal by the extremists.

The Observatory says more than 180 civilians have been killed in the flare-up since April 30, and the United Nations has said tens of thousands have fled their homes.