BEIRUT (AP) — Syrian rebels on Wednesday seized control of a hospital in the northern city of Aleppo that was used as a base for the area by their al-Qaida rivals, activists said.

The capture of the hospital was a boost for the rebels, who only the day before saw 20 of their fighters killed in an al-Qaida suicide car bombing in the northern city of Darkoush, said the British-based Syrian Observatory for Human Rights.

It also underscores the intensity of the rebel infighting that has raged for days between Syrian rebels and their one-time allies, fighters from the extremist Islamic State in Iraq and the Levant.

Also in Aleppo, the Observatory said a series of government airstrikes in two rebel-held suburbs late on Tuesday night killed 19 people. There were no further details. The government in Damascus did not comment on the bombings.

The two main rebel camps in Syria fighting against President Bashar Assad's troops — a chaotic array of rebel brigades and the al-Qaida-linked group — turned their guns on each other last Friday. The clashes have since become the most serious rebel infighting since the uprising against Assad began in March 2011.

The rebel-on-rebel fighting began after tensions, which had simmered for months, erupted into the open after reports that the al-Qaida fighters had tortured and killed a popular doctor.

It has since spread from the northern province of Aleppo to nearby Idlib and to the province of Raqqa. At least 300 people have been killed in the infighting, said Rami Abdurrahman, the head of the Observatory.

The clashes add another layer of complexity to the Syrian conflict, less than three weeks ahead of a planned international peace conference to try to resolve the civil war.

Syrian rebels seized the hospital in Aleppo's Qadi Askar quarter that the al-Qaida fighters had overrun months ago and used as their main compound or base for the area, said the Observatory, which relies on a network of activists on the ground.

The Observatory said there were reports, still unconfirmed, that dozens of detainees held by the extremists had been freed.

One of the most pressing issues in the rebel infighting is the fate of dozens of Syrian and foreign reporters, media activists, aid workers and civilians abducted and held by the al-Qaida fighters since they fanned into the area in March.

There are fears for the fate of the detainees as the fighting rages and as the al-Qaida group seeks to extoll revenge on their rivals.

On Tuesday, the Observatory and other groups reported that at least four activists detained in the Aleppo hospital had been killed.

As the rebel infighting continued, so did clashes between Assad's forces and rebels.

In Douma, a town close to the Syrian capital of Damascus, three people and a child were killed and several were wounded after a government airstrike targeted a house on Tuesday, reported the Observatory and another activist group, the Local Coordination Committees.

Dramatic footage of the aftermath of the strike was uploaded to social media networks. It corresponded with the Associated Press' reporting of the event.

"Be patient, little one, be patient!" a man is seen in one video, calling out to a child who was heard wailing under the rubble of a smashed house. Other men are seen furiously digging to pull out the victims.

Minutes later, a toddler screams as he is seen being pulled out from under the rubble. Another man is seen carrying a dust-covered, lifeless small body to nearby medics who then try to resuscitate the child.