(Adds comment from interior official)

By Faisal Aziz

ISLAMABAD, July 6 (Reuters) - Islamist students holed up in an Islamabad mosque fought gunbattles with Pakistani security forces on Friday after the militants' leader said he and hundreds of his followers would rather die than surrender.

Earlier, gunmen fired at President Pervez Musharraf's plane as it took off from Islamabad's military airport, a security officer said. The government said there appeared to be no link between the shooting and Musharraf's flight to inspect flood damage in the south.

Adding to a sense of foreboding over risks posed to stability by militants, a suicide bomber killed six soldiers in a northwest region where the Islamist in the mosque have allies. There was no indication the bomber was acting in support of the mosque, but it is known to have supporters in the region.

Musharraf has not commented publicly on the siege at Islamabad's Red Mosque, or Lal Masjid, but has urged security agencies to allow time for parents to take children out of a madrasa, or school, in the mosque compound.

At least 19 people have been killed in clashes that erupted outside the mosque on Tuesday. The compound has been under siege by hundreds of troops and police.

Interior Ministry Secretary Syed Kamal Shah appealed to the Taliban-supporting cleric leading the militants, Abdul Rashid Ghazi, to give up and said he would be treated humanely.

"There are many precious lives in his hands ... he should show courage and come out," Shah said.

"If he is concerned about his safety, we are ready to give any guarantees." Suicide bombers were in the mosque and suicide bomb vests had been distributed, he said.

Tension between authorities and the mosque had been rising since January when students, most of whom are in their 20s and 30s, launched a defiant campaign to press for various demands including action against vice.

Water, gas and power to the mosque have been cut and food was scarce, said a boy, one of about 20 people who left it on Friday.

Nearly an hour of intense fire erupted at around 6 p.m. (1300 GMT). Two loud blasts shook the leafy neighbourhood that has been under curfew since Tuesday, sending smoke into the air. Authorities said on Thursday they had blasted holes in the compound's walls.

"ASSASSINATION ATTEMPT"

Referring to the Musharraf plane incident earlier, an intelligence officer, speaking on condition of anonymity, said the shots fired from a house close to Islamabad airport had been an unsuccessful attempt on the president's life.

"There was an attempt, that was missed," said the officer.

U.S. ally Musharraf, who came to power in a military coup in 1999, survived two assassination attempts by al Qaeda-linked militants in 2003.

A Reuters photographer saw two machineguns mounted on the flat roof of the house. The Interior Ministry said two anti-aircraft guns had been found but had not been fired. A 7.62 mm sub-machinegun that was also found had been fired.

"There does not appear to be any linkage between the incident and the president's flight," it said.

Ghazi has said he and the followers were willing to surrender but set conditions, including safe passage. The government insisted he release women and children it says he is holding as human shields, and surrender unconditionally.

But Ghazi told Geo TV he would not bow to pressure: "We can be martyred, but we will not court arrest."

A boy who surrendered after sneaking out of the mosque said older students were forcing younger ones to stay. The stench from dead bodies hung in the air, Ashraf Swati, 15, told Reuters.

Militants later fired on some parents approaching the mosque in the hope of collecting their children, wounding one.

Ghazi's elder brother and chief cleric, Abdul Aziz, was caught on Wednesday trying to flee disguised in a burqa. He later called on followers to give up. About 1,200 students have come out. Aziz said there were 850 students inside, Ghazi said 1,900.

Many Pakistanis welcomed the government's move against a movement reminiscent of the Taliban in neighbouring Afghanistan, and symptomatic of the religious extremism seeping into cities from tribal border areas.

Moderate politicians and the media had urged Musharraf to act sooner but he cited concern about bloodshed. (Additional reporting by Augustine Anthony)

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