A gun battle erupted in India's heavily guarded Parliament complex near mid-day Thursday. All lawmakers are safe, but at least five armed intruders and six security personnel are dead.

The gun battle erupted an hour and a half after Parliament convened Thursday. Initial reports say at least five armed men tried to enter the complex at an entrance for lawmakers, leading to a shootout with security forces.

Hundreds of rounds were fired for more than half an hour during the gun battle between security personnel and the attackers. Reports say most or all of the attackers were killed. The complex is being combed to ensure no gunmen remain inside. The army and paramilitary commandos have surrounded the building.

Parliament had been adjourned when the attack took place - but at least 300 lawmakers including senior ministers were inside the building when gun battle erupted. Parliamentary Affairs Minister, Pramod Mahajan says all members of parliament are safe.

Speaking to an Indian television network (Star News) Home Minister Lal Krishna Advani suggested it could have been a suicide attack - but did not identify who was responsible. "Howsoever secure you make your country, your institutions, fidyaeen [suicide] attacks are of a nature which have breached even the Prime Minister's house when we lost Mrs. [Indira] Gandhi, which have breached even the Pentagon," says Mr. Advani.

Mr. Advani compared the attack on Parliament to a previous attack on the state assembly building in Jammu-Kashmir state by suspected Islamic militants.

Security has been tightened in New Delhi. Police have halted traffic on major roads leading to the parliament building, which is located in the central part of the city.

India is wracked by separatist militant violence - but this is the first time an attack has been launched on the heavily-guarded parliament complex.