At least five people were killed Monday when attackers stormed a police station near India's border with Pakistan, triggering a gunbattle that lasted almost 12 hours and stepped-up security in parts of the country.

Police said security forces were combing the building where the unidentified gunmen wearing army uniforms had been holed up since the dramatic early-morning assault in the northern state of Punjab.

"The operations are over. All our senior officers are inside and a combing operation is on," local police spokesman Rajvinder Singh told AFP.

Police earlier said three civilians and two police officers had been killed.

The fate of the attackers was not immediately clear but an AFP reporter at the scene said the fierce gunfire that had continued throughout the day had ended, allowing police to enter the building.

Local government officer Abhinav Trikha said "three to four attackers" had opened fire on a bus and hijacked a vehicle before storming the police station.

Five live bombs were recovered from nearby railway tracks, forcing train services to be cancelled.

Home Minister Rajnath Singh said he had ordered increased security on the border with Pakistan, although the identity of the attackers was not immediately clear.

A number of other states were also reported to be on high alert.

National problem

It was the first major attack in India's Punjab for more than a decade and the state's Chief Minister Prakash Singh Badal blamed a lack of security on the border.

"This militancy is a national problem, not a state problem, so it needs to be tackled with a national policy," he told reporters.

"If prior intelligence input had been given, they should have properly sealed the borders."

Insurgents frequently target police in the volatile Kashmir region, which is divided between arch rivals India and Pakistan and claimed in full by both.

But neighbouring Punjab, a majority-Sikh state, has largely been spared the violence that has plagued Indian Kashmir.

An armed rebellion for a separate Sikh homeland erupted in Punjab in 1983 but waned in the early 1990s.

About 50,000 people died in that conflict, which India blamed at the time on Pakistan.

Some media reports suggested the attackers behind Monday's assault in Gurdaspur may have crossed into Punjab from Kashmir.

Monday's attack comes weeks after Indian Prime Minister Narendra Modi and his Pakistani counterpart Nawaz Sharif spoke for about an hour during a summit in Russia.

The meeting raised hopes of an improvement in perennially difficult relations, but was swiftly followed by a flare-up in violence along the de facto border in Kashmir.

India regularly accuses Pakistan's army of providing covering fire for rebels who infiltrate across the border and then mount attacks in the Indian sector of Kashmir.

The two countries have fought three wars since independence from Britain in 1947, two of them over the Himalayan region.