At least four more people have died amid renewed battles between students and security forces at a mosque in the Pakistani capital Islamabad, taking the death toll to 16.

A student at the Lal Masjid, or Red mosque, was killed in shooting early Wednesday and three others died of injuries sustained a day before, hospital officials said.

"We have received a dead body this morning. The victim is a 22-year-old who received gunshots," a hospital doctor said.

Pakistani security forces imposed a curfew in the neighborhood where the mosque is situated and troops threw a cordon around the mosque.

Negotiations to end the siege of the mosque, brokered by independent clerics, "appear to heading nowhere", Abdul Rashid Ghazi, deputy leader of the students, said.

"First they should stop this action and only then there could be any negotiations," he said.

Deaths in hospital

Three other wounded students were treated at the state-run Pakistan Institute of Medical Sciences early on Wednesday, a doctor at the hospital's emergency ward said.

Three people, critically wounded in the previous day's fighting, died overnight, the doctor said.

Three others with serious bullet injuries were brought to another state-run hospital, the Polyclinic, a doctor there said.

 "One of them is undergoing surgery at the operation theatre," he said.

As well as the deaths, more than 120 were wounded in the fighting on Tuesday, officials and hospitals said.

Violence began at the mosque when around 10 students, armed with staves, attacked a police party which was taking up positions around the mosque.

 Police then fired teargas at the students, prompting an exchange of gunfire lasting around 15 minutes, witnesses said.

 Appeals were made on the mosque's loudspeakers for residents of Islamabad to come to the mosque and help the students and 'mujahideen'.

PHOTO CAPTION

Government forces seal off the area surrounding the mosque