A suicide attack believed to have been carried out by the Nusra Front caused a major explosion in Idlib province on Sunday, a video uploaded to a social media website appears to show.

The video purports to show al-Nusra fighters, al Qaeda's wing in Syria, targeting the national hospital in the town of Jisr al-Shughour.

Reuters is unable to independently verify the contents of the video, which was obtained from a social media website.

However, Jisr al-Shughour was overrun last month by insurgents, including the Nusra Front.

An army source told Reuters that its troops were now several kilometers away from the besieged hospital, the last remaining army foothold in the town.

The UK-based Syrian Observatory for Human Rights, which tracks violence across Syria, said insurgents got into one of the hospital buildings on Sunday, after a suicide bomber from Nusra Front blew himself up at dawn.

Pro-government sources said the army had repulsed the attack.

Rebels had so failed to storm the hospital despite repeated suicide bombings and intense mortar shelling from nearby positions.

The compound is situated on a hilltop overlooking a main highway and has several underground levels that have sheltered the troops from the rebel shelling.

The Syrian army is determined to achieve a victory, to restore morale and regain momentum against the rebels, after losing Jisr al-Shughour, and on March 28, the provincial city of Idlib. Large parts of the rich agricultural province are now in rebel hands.