Several explosions were heard near a radical mosque besieged by security forces in the Pakistani capital Thursday, hours after its top cleric was captured trying to sneak out of the complex under a woman's burqa.

It was not immediately clear what caused a series of heavy blasts which lit up the sky near Islamabad's Lal Masjid, or Red Mosque, before dawn on Thursday. Troops ringing the mosque pushed reporters far back from the area as gunfire broke out.

• Click here for photos of the mosque siege.

Farooq Anwar, a city police official, said security forces responded to shots fired from the mosque compound, but he had few details. Police were using loudspeakers to urge the militants to surrender, he said.

President Gen. Pervez Musharraf deployed the army Wednesday to subdue militants holed up in the mosque, whose clerics have defied the government for months with a drive to impose a Taliban-style version of Islamic law in the city.

The tensions had erupted into a daylong battle on Tuesday between security forces and students — some of whom were heavily armed and masked. Officials have reported at least 16 people killed and scores injured.

The government on Wednesday ordered the militants to lay down their arms and surrender, and hundreds, mainly male and female students from the mosque's madrassas, or religious schools, obeyed the call, streaming from the compounds into the relieved arms of worried relatives.

A security official, who spoke on condition of anonymity because he was not authorized to talk to the media, said authorities captured the mosque's top cleric, Maulana Abdul Aziz, on Wednesday evening after a female police officer checking women fleeing the area tried to search his body, which was concealed by a full-length black burqa.

The officer began shouting "This is not a woman," the official said, prompting male officers to seize him. "The suspect later turned out to be the mosque's chief cleric," the official said.

An AP Television News cameraman saw plainclothes police bundling the gray-bearded cleric into the back of a car, which sped away.

"They have no options but to surrender," said Javed Iqbal Cheema, a government spokesman. "The government is not into dialogue with these clerics."

The mosque's deputy leader, Abdul Rashid Ghazi, said earlier in the day that he was prepared to talk with the government, but added, "We will continue to defend ourselves."

The city's deputy administrator, Chaudhry Mohammed Ali, said more than 1,000 had surrendered. All women and children will be granted amnesty, but males involved in killings and other crimes as well as top mosque leaders will face legal action, said Deputy Information Minister Tariq Azim.

Minister of Information Mohammed Ali Durrani said there could be "a few hundred" or more people remaining inside the mosque complex. It was unclear how many were militants.

One who decided to give up, 15-year-old Maryam Qayyeum, said those who stayed in the seminary "only want martyrdom."

"They are happy," she said. "They don't want to go home."

Qayyeum said mosque leaders were not trying to stop students from giving up. But her mother, who had come to take her home said, "They are making speeches. They want to incite them."

Johar Ali, 20, who had come to the mosque to support the militants several days ago, said there were still hundreds inside. But Ali did not report seeing any suicide bombers, who the mosque leaders claimed were ready to launch attacks.

A senior government spokesman, Anwar Mahmood, said 16 people were killed Tuesday, though he declined to give a breakdown of the victims. Earlier, the government said they had included militants, innocent bystanders, a journalist and members of the security forces.

Ghazi told The Associated Press that 20 of his students had been killed by security forces, including two young men climbing to the top of the mosque for prayers Wednesday.

A young woman was also shot and wounded on the roof of the women's seminary, he said. "She was shot by sniper fire. They are shooting directly at us," he said in a telephone interview.

In the past six months, the clerics have challenged the government by sending students from the mosque to kidnap alleged prostitutes and police in an anti-vice campaign.

The bloodshed has added to a sense of crisis in Pakistan, where Musharraf — a major ally of U.S. President George W. Bush — already faces emboldened militants near the Afghan border and a pro-democracy movement triggered by his botched attempt to fire the country's chief justice.

The mosque siege has sparked street protests in several other cities organized by radical religious parties.

On Wednesday, officials said a suicide car bomber rammed a vehicle into a Pakistan army convoy near the Afghan border, killing five soldiers and five civilians. In northwestern Pakistan, unidentified assailants fired a rocket at a police station, killing one officer and wounding four, and an explosive killed four people and injured two district officials.

It was not known if the incidents were linked to the mosque crisis.

• Click here for photos of the mosque siege.