By IRNA
Islamabad : Security forces and hundreds of students holed up inside Pakistan's Lal Masjid (Red Mosque) in Islamabad xchanged fire, seen the heaviest in the three day standoff.
Four gunship helicopters were seen flying at low altitude over the mosque and seminary complex.
The security forces asked the cameramen, photographers and journalists to move back from their positions around 500 meters from the Lal Masjid.
TV channels reported that the forces fired mortars to blow up walls of the complex to find ways to enter the premises as a major operation is launched.
The authorities had set a 12:30 p.m. deadline to few hundreds of male and female students to surrender but their leader Abdul Rashid Ghazi, also the acting head of the Lal Masid, said they would not surrender.
Pakistani troops tightened their grip around the mosque and the seminary Jamia Hafsa.
The forces fired tear gas shells inside the mosque and seminary complex.
The students responded with automatic gun shots, according to TV channels.
The troops set off blasts outside the mosque, as negotiations have failed so far to solve the crisis amicably.
TV channels reported that more paramilitary force and police Special Forces were called in an apparent major action.
Authorities have confirmed 16 people have died in recent clashes at the complex.
The students handed over two more bodies Thursday morning. This brought the number of the dead to 18.
The government said more than 1,200 students had surrendered till Wednesday, and that their details were being recorded at a camp set up near the mosque.
Following the expiry of 12:30 p.m. local time deadline on Thursday, some 150 more students were seen giving themselves up.
The latest confrontation reportedly started when security forces tried to place barriers around the mosque last week.
On Tuesday, the students traded gunfire with security forces for the first time.