Pakistani security forces have fired a series of "warning blasts" near Islamabad's Red Mosque, or Lal Masjid, in a bid to step up pressure on students inside to surrender, a security official said.

About eight explosions and sporadic gunfire were heard during a period of 20 minutes, witnesses said.

"They were warning blasts. We have not yet entered the mosque," said the official.

The mosque started an anti-vice campaign in Islamabad six months ago with its students abducting women they said had carried out "immoral acts".

Musharraf has accused the mosque of sheltering al-Qaeda members.

Chaudhry Mohammed Ali, the city's deputy administrator, said more than 1,000 people inside the mosque had surrendered.

Amnesty offered

Tariq Azim, the deputy information minister, said all women and children would be granted amnesty, but men involved in killings and other crimes as well as mosque leaders would face legal action.

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

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

President Musharraf has said each of those who surrendered would receive 5,000 rupees ($83).

On Wednesday, a senior cleric at the mosque, Abdul Aziz Ghazi, was arrested by Pakistani security forces, after trying to escape the compound.

 'Unusual demeanor'

 Mohammad Ali Durrani, the information minister, said: "He was trying to escape with the girls and was wearing a burqa."

Television footage showed security officials dragging Aziz towards a black car before he was driven away. Officials said he was caught in a screening centre set up to check people leaving the mosque.

 "He was the last in a group of women all wearing the same clothes. He was wearing a burqa that also covered his eyes," a senior security official told AFP.

 "Our men spotted his unusual demeanor. The rest of the girls looked like girls but he was taller and had a pot belly."

Police enforced a curfew and a series of deadlines to end the standoff after clashes on Tuesday left up to two dozen people dead.

'Uncompromising attitude'

As the first deadline passed on Wednesday morning, Abdul Rashid Ghazi, the brother of the captured cleric, said he was prepared to talk with the government but added: "We will continue to defend ourselves".

He said the mosque had enough supplies to carry on "until God wants".

But the government said it would not open dialogue with the mosque's clerics.

"The prime minister made it clear that time for negotiations with the management of Lal Masjid had lapsed due to the obstinate and uncompromising attitude of the Ghazi brothers," the government said.

About 5,000 students, most from poor areas of Pakistan, are registered at the mosque and its affiliated schools.

PHOTO CAPTION

Security forces set up screening centers to check people leaving the Red mosque