Heavy explosions were heard around the besieged Lal Masjid complex where several hundred militants are holed up and engaged in a tense stand-off with Pakistani security forces.

The militants are led by the Lal Masjid deputy head cleric Abdul Rashid Ghazi, who said that he would not surrender before the authorities.

Following the blasts, clouds of smoke formed over the area which could be seen from a long distance. It was not clear what caused these explosions.

Top government officials, in a live television press conference, appealed to Ghazi to give himself up and release scores of women and children, who are still inside the Masjid.