The blast tore a 2m (6ft) hole through a wall surrounding the UN building.

The blast had been caused by an explosive device. There have been no reports of casualties.

No group has so far claimed responsibility for the explosion. Offices of Hamas' intelligence service and a prison are also nearby.

The Israeli military said it had not been operating in the area at the time.

Security forces in the Hamas-run Palestinian territory have cordoned off the area and denied access to journalists.