A Syrian child receives treatment at a makeshift hospital after an airstrike on a vegetable market in Maarat al-Numan, in Syria's northern province of Idlib on April 19. (Mohamed Al-Bakour/AFP/Getty Images)

Even though they strongly oppose militants linked to al-Qaeda, residents of a rebel-held town in northwestern Syria on Tuesday faced devastating airstrikes from pro-government warplanes that killed at least 37 people, according to activists and a monitoring group.

The air raids targeted an area crowded with civilians in Maarat al-Numan, killing and wounding scores, including women and children, according to the Syrian Observatory for Human Rights.

“The death toll is almost certain to rise,” said the head of the Britain-based Syrian Observatory, who uses the alias Rami Abdulrahman. He described the attack as a “massacre.” His group operates a team of activists in Syria that monitors the conflict.

Mohammad Karkas, a media volunteer for local rebel groups in Maarat al-Numan, said the death toll could be as high as 51. A warplane targeted the town’s main market with two rockets, cutting down scores of people — including families — as they shopped for fruits and vegetables, he said.

“There were charred bodies all over the street. Their insides were torn inside out,” he said, noting that local medical facilities were overwhelmed with the wounded. “There were people who lost arms and legs.”

A woman tends to a wounded Syrian man at a makeshift hospital after an airstrike on Maarat al-Numan on April 19. (Mohamed Al-Bakour/AFP/Getty Images)

The bombing struck amid faltering peace talks in Geneva and the apparent collapse of a partial cease-fire, initiatives that have received backing from both the United States and Russia. Even though they are divided over the civil war, the two powers have pursued intensified diplomacy in recent months to end a civil war that has killed 250,000 people and displaced millions.

It was unclear whether the raid was carried out by government warplanes or aircraft operated by Russia, which intervened militarily in the Syrian conflict last year to bolster its ally, President Bashar al-Assad, against rebel forces. The United States backs Assad’s moderate opponents.

Footage posted by activists on social media, which could not be independently verified, shows Maarat al-Numan’s formerly bustling market area reduced to rubble and smoldering ruins. Other images showed stunned residents limping away from the attacked area, as well as emergency responders carrying away the wounded.

For critics of Assad, Tuesday’s raid on the town in northwestern Idlib province further demonstrates how his forces­ deliberately target civilians in the country’s devastating war. Some critics charge that Assad also seeks to empower extremists as a way to delegitimize the rebellion against his rule.

Since early March, residents of the town about 170 miles north of Damascus have held large demonstrations against Jabhat al-Nusra, al-Qaeda’s affiliate in Syria, forcing the radical group to withdraw from the town. The departure of its militants from the area — where they had once roamed the streets with virtual impunity — demonstrated that moderate voices in the Syrian conflict have not been silenced, analysts and opposition supporters said.

A Syrian man stands amid debris following an air strike on a vegetable market in Maaret al-Numan on April 19. (Mohamed Al-Bakour/AFP/Getty Images)

“This massacre of innocents in a market place in Maarat al-Numan shows the true face of the Assad regime — utterly brutal, totally careless of human life,” said Salem al-Meslet, a spokesman for the opposition High Negotiations Committee delegation to the peace talks in Geneva.

On Monday, the HNC suspended its participation in the talks, citing alleged intransigence by the government delegation, especially over the issue of Assad’s future.

“Assad is telling the world he has no interest in diplomacy for peace, but is determined to go on killing Syrians with impunity,” Meslet said in a statement.

The partial cease-fire, which took effect Feb. 27, had reduced hostilities enough to allow public rallies in opposition areas against Syria’s government. Jabhat al-Nusra and the Islamic State were not included in the cease-fire.

In Maarat al-Numan, those demonstrations quickly escalated into protests against Jabhat al-Nusra over what residents said were increasingly heavy-handed measures imposed by the group. These included the violent treatment of religious minorities and forcing residents to obey strict fundamentalist rules, such as the mandatory covering of women in public places.

The group also angered residents after it attempted to disperse anti-government rallies and attacked local rebel fighters.

Mohammed Alaa Ghanem, a senior political adviser at the Syrian American Council, said Jabhat al-Nusra would probably try to exploit Tuesday’s attack by attempting to demonstrate its anti-Assad bona fides to residents. The al-Qaeda affiliate has a reputation for effectiveness in battles against Syrian government ­forces.

“These kinds of attacks make it impossible for people to rise up against extremism, denying them any chance to build a civil society and a sense of normalcy in their communities,” he said.

Imad Salamey, a political science professor at the Lebanese American University, said Tuesday’s bombings further demonstrate how extremist groups and the Syrian government find common cause in trying to marginalize moderate opposition forces.

“This just shows again how both extremes in the Syrian conflict — the regime and the radical Islamists — feed off each other and need each other to survive,” he said.

Zakaria Zakaria in Istanbul contributed to this report.