The top cleric at a besieged mosque in the Pakistan capital accused security forces on Saturday of killing more than 70 of his students, but said he and his supporters preferred martyrdom to capture. Explosions and intense gunfire continued overnight and Saturday as thousands of troops ringing the Lal Masjid, or Red Mosque, attempted to end a standoff but held back from an all-out assault. Although the government says only 19 people have died since Tuesday, Abdul Rashid Ghazi, the mosque's defiant cleric, told the local Geo television channel that more than 70 of his students had been slain by government gunfire. "There are 70 to 80 bodies of our students," he said in a claim which could not be independently verified. The siege has added to the risks facing President Gen. Pervez Musharraf, who must cope with a gathering storm of domestic Islamic extremism as well as a popular backlash from his bungled attempt at firing the country's chief justice. Authorities Saturday were also investigating a possible assassination attempt against him, after shots were fired as Musharraf's plane took off from a military base near the capital. Musharraf was flying from Chaklala Air Base in Rawalpindi on Friday morning when shots rang out from a neighborhood that lies directly under the flight path, officials and witnesses said. If confirmed, the attack would be at least the fourth attempt on Musharraf's life since his decision to side with the United States in its war on terror enraged Taliban and al-Qaida-linked radicals in Pakistan. It was not clear whether the incident was linked to the siege, but street protests organized by radical Islamic groups have been staged daily since the government began its strike against the mosque Tuesday. Troops surrounded the mosque and an adjoining women's seminary after tensions between government security forces and Islamic students - who have sought to impose Taliban-style rule in the city - erupted into deadly street clashes.