BOMBAY, India (AP) _ Hundreds of policemen were still trading gunfire with Sikh militants in a Bombay shantytown today after at least six people were killed in fighting that began with a police raid, authorities said.

Sikh militants, fighting for an independent nation in the northern state of Punjab, have often staged attacks in nearby states, but they have rarely operated in places as far south as Bombay.

The city, India's largest and the capital of the western state of Maharashtra, is about 780 miles southwest of Punjab.

A Bombay police spokesman said four militants, one police constable and one resident of the Bhandup slum in eastern Bombay were killed overnight in the gunbattle. He said four residents and four police officers were wounded.

Intermittent firing continued today, more than 14 hours after it started at 4 p.m. Wednesday, said the spokesman, who cannot be identified under police rules.

City police chief S. Ramamurthi said it was not immediately known how many militants were hiding in the shantytown. He said police had been tipped off to the militants' whereabouts.

Earlier Wednesday, two other Sikh militants were killed when a bomb they were carrying on a motorcycle exploded in another part of Bombay. Ramamurthi said an AK-56 assault rifle, two pistols and four grenades were recovered from the dead militants.

Press Trust of India news agency said two of the militants killed in the overnight fight were wanted in several cases in Punjab.

It was not immediately clear whether the shantytown resident was killed by the militants or if he died in crossfire.

Anti-terrorist policemen armed with automatic guns kept overnight vigil with searchlights around the shantytown of about 5,000 huts made of corrugated iron sheets along narrow lanes.

In January, police shot and killed two Sikhs in another eastern suburb of Bombay after a fierce gunbattle. It was the first time Sikh extremist violence had spilled over to Bombay.

Police say the rebels come to Bombay, India's commercial capital, to extort money from Sikh businessmen, either by threat or by playing on their sympathy for the separatist cause.

Sikhs are in a slight majority in Punjab, but nationwide they form just 2 percent of India's 844 million people. Hindus account for 82 percent.