Syria's best-known mosaic museum in the northern rebel-held town of Maaret al-Numan has been seriously damaged in a regime barrel bomb attack, according to archaeological experts.

The Association for the Protection of Syrian Archaeology said the museum "suffered serious damage caused by two explosive-packed barrels dropped on Monday by Syrian army helicopters."

The non-governmental organisation published pictures of the museum, located in an ancient Ottoman caravanserai, showing entire walls once covered with mosaics collapsed into rubble.

It said that several mosaic panels had been damaged in the eastern portico of the museum, including at least two that were knocked off their display by the force of the blast.

Other pieces were damaged by shrapnel and the pictures published by APSA on its website showed large holes gouged into an oval mosaic with a zig-zag pattern.
The museum building and surrounding complex, including a historic mosque, were also badly damaged, according to the APSA, with pictures showing several pillars destroyed and sections of roof that had caved in.

Reached by phone in Damascus on Saturday, the head of Syria's antiquities, Maamoun Abdulkarim, acknowledged the damage at the museum, but declined to say who was responsible.

This is "a new tragedy for Syrian heritage", said Abdulkarim and called for the country's museums to be "neutral zones" in the war.

"No one, from any side, should harm that which forms our country's history," he said.

The United Nations last year warned that nearly 300 sites of incalculable value for Syria and human history have been destroyed, damaged or looted in the country's conflict.

The warning, based on satellite imagery, followed repeated statements of concern from archaeologists and other experts about the damage being done to Syria's historic sites and the rise in looting of antiquities.

More than 230,000 people have been killed in Syria since the conflict began in March 2011 with anti-government demonstrations before spiralling into a war after a regime crackdown.