A Free Syrian Army fighter runs with his weapon during clashes with forces loyal to President Bashar al-Assad at the frontline in Handarat area, north of Aleppo, on Thursday.

Reuters/Beirut

Insurgents on Friday seized a hospital from Syrian government forces which had been besieged there since late April, the Syrian Observatory for Human Rights said, another gain by rebels who have dealt a series of blows to President Bashar al-Assad.

Syrian state TV said soldiers holed up in the Jisr al-Shughour hospital in Idlib province had been freed, saying they had managed to "break the siege" in an operation coordinated with air strikes and artillery bombardment.

The al Qaeda-linked Nusra Front, an insurgent group involved in the offensive, said government forces had fled. "The Mujahideen are pursuing them," a Twitter feed affiliated to the group reported.

Assad has lost large parts of Idlib province to insurgents since late March, when the provincial capital fell to rebels who have organised themselves under the banner of the "Army of Fatah", or the army of Islamic conquest.

Assad had himself publicly addressed the situation at Jisr al-Shughour hospital two weeks ago, saying the army would reinforce the besieged troops there and describing them as heroes.

The losses in the northwest have been compounded by dramatic advances by the Islamic State jihadist group into government-held areas of central Syria. The group seized the ancient city of Palmyra, or Tadmur, on Wednesday.

It has also taken control the last government-held border crossing with Iraq, after Syrian security forces withdrew.

The Observatory said dozens of Syrian troops had managed to escape from the hospital, where the insurgents were in complete control. Rami Abdulrahman, who runs the Observatory, described it as a blow to the morale of the regime, after it had sent reinforcements there including allied foreign militia.

Jisr al-Shughour is seen as strategically important because of its proximity to the Mediterranean coastal areas that form the heartland of Assad's minority Alawite sect.

The Observatory reported heavy fighting overnight in the Jisr al-Shughour area in what appeared to be an effort by the Syrian military and allied militia to advance and break the siege. Syrian war planes mounted at least 22 air strikes in the area, with helicopters dropping barrel bombs, it said.

A photo posted on the Nusra Front-affiliated Twitter feed showed dozens of people streaming out of a heavily damaged building said to be the hospital. A caption said they had been "humiliated and routed by the force of the siege".