The civilians, including a dozen people at a busy market, were killed in the rebel and opposition-held Idlib since Tuesday midnight, the Syrian Observatory for Human Rights says.
Syrian regime air strikes killed 23 civilians, including a dozen people at a busy market, as fierce fighting raged for the rebel and opposition-held northwest, a war monitor said on Wednesday.
Regime forces battled to repel a counter-offensive around the town of Kafr Nabuda that has left 70 combatants dead in 24 hours, the Syrian Observatory for Human Rights said.
The Hayat Tahrir al-Sham alliance, led by Syria's former Al Qaeda affiliate, controls a large part of Idlib province as well as adjacent slivers of Aleppo, Hama and Latakia provinces.
The region is nominally protected by a buffer zone deal, but the regime and its ally Russia have escalated their bombardment in recent weeks, seizing several towns on its southern flank.
At least 12 people were killed and another 18 wounded when regime warplanes hit the Idlib province town of Maarat al Numan around midnight (2100 GMT) on Tuesday, the Observatory 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 bombardment blew in the facades of surrounding buildings, and ripped through the flimsy frames and canvas of stalls in the market square, an AFP photographer reported.
The total death toll in Idlib since April 30th is now 611 people, including 200 civilians. SOHR
The US State Department suspects the regime of using chemical weapons during its current offensive.
Washington says it will carry out reprisal attacks if the use of chemicals is verified.
The White Helmets rescue group in Syria has told TRT World it's heard reports of a chlorine gas attack on a village in Latakia.
The group has collected evidence including debris from munitions, as well as soil samples.
TRT World's Ali Mustafa has more from Gaziantep, near Turkey's border with Syria.
Syrian regime quells militant attacks
Regime forces on Wednesday morning repelled three big attacks by militants in Syria's Idlib province, the Russian Ministry of Defence said.
It said in a statement that 500 Nusra Front militants, seven tanks, and about 30 pickups mounted with heavy machine guns had taken part in the attacks.
The ministry said that Syrian militants based in Idlib had also launched a missile attack on Russia's Hmeymim air base on Wednesday, but that their missiles were either shot down or did not reach their target.
A militant alliance led by Syria's former Al Qaeda affiliate, Hayat Tahrir al Sham (HTS), controls a large part of Idlib province as well as adjacent slivers of Aleppo, Hama and Latakia provinces.
Russia and Turkey inked the buffer zone deal in September to avert a regime offensive on the region which threatened humanitarian disaster for its three million residents.
Bashar al Assad's regime has renewed its bombardment of the region since HTS took control in January.
Russia too has stepped up its air strikes in recent weeks.
US envoy Jeffrey calls for ceasefire
A ceasefire is needed in Idlib province where there has been a recent upsurge in violence, and the United States is working towards halting the clashes, which have put tremendous pressure on civilians there, US envoy James Jeffrey said on Wednesday.
"What we really need in Idlib and throughout the country is a ceasefire," Jeffrey, US special representative for Syria engagement and special envoy to the global coalition to defeat the ISIS militant group, said at a House of Representatives Foreign Affairs Committee hearing.
"These conflicts, back and forth exchanges....just put tremendous pressure on civilians, they raise the specter of nation-to-nation clash," he said. "So we're very much engaged in trying to get this stopped and get it back to the ceasefire we had basically since September."