Pakistani troops stormed the Lal Masjid complex in Islamabad early on Tuesday morning after talks with radicals to end the weeklong standoff broke down, triggering a heavy gun battle, which left 50 militants and eight soldiers dead.

Heavy gunfire erupted and loud blasts were heard as Operation Silence was launched at 4 am with commandos surrounding the mosque, where militants are believed to be holding 150 hostages, from three sides.

20 children escaped as the operation began and were taken in the care of security forces. Fierce fighting raged at the religious school and library in the compound where hundreds of women and children were believed to be present.

Deputy administrator of the masjid Abdul Rashid Ghazi and his supporters, believed to have taken shelter in the bunkers built in the basement of the mosque, are putting up a stiff resistance, Defence Ministry spokesman Major General Waheed Arshad told reporters.

"The militants are using small arms and grenades. They are in the basement," he said adding, "we are facing resistance from the basement. Such an operation could take three or four hours."

"According to my information part of the mosque has been cleared but heavy fighting was on in madrassa," he said.

The militants are believed to be armed with machine guns, rocket launchers, hand grenades and petrol bombs.

Fifty militants and eight soldiers were killed during the operation, the military said.

As the explosion began rocking the besieged mosque complex, Ghazi spoke briefly to TV channels and blamed the government for the failure.

Ghazi said he was ready to leave as suggested by the government, but at the same time insisted that clerics and media should visit the mosque complex to prove his claim that no foreign militants or heavy weapons were there.

State-run PTV said there was direct to direct confrontation between commandos and militants.

"It is the final push to clear the mosque of armed militants," Arshad said.

He said he has no information about the claim of Ghazi that his mother has been killed. Asking the residents of the capital not to come out or go on to their terraces, he said they could be hit by shrapnel and stray bullets.

He said estimates are that about 200 to 300 militants were holed up in the complex and the troops hope to finish the operation as early as possible.

Emergency has been declared in all the hospitals in Islamabad and nearby Rawalpindi and doctors and other medical staff were kept on standby before the operation began.

The operation was launched as soon as ruling Pakistan Muslim League-Q President Shujaat Hussain in a brief nationally televised press conference said talks to find out a peaceful solution to the standoff had failed.

Hussain said he was never disappointed so much in life that an agreement could not be reached even after the government showed maximum flexibility.

Earlier reports said the government had discussed providing a safe passage to Ghazi, his family as well as others and confine him to house arrest in his native village in Balochistan.

The operation came at the end of a seven-day standoff during which over 1,300 boys and girls holed up in the madrassa surrendered. The government has accused Ghazi and militants of holding a large number of women and children as hostages to use them as human shields.

Government has said that several foreign militants, perhaps belonging to Al Qaeda [Images], were holed up. President Pervez Musharraf [Images] himself said militants of Jaish-e-Mohammed were also holed up there.

Officials said that militants appeared to have taken control of the mosque and the leadership from Ghazi.