Gunfire and blasts were heard on Sunday at an Indian Air Force base attacked by militants a day earlier, as security forces hunted two gunmen still at large in the sprawling facility near the border with Pakistan.

A senior federal police official confirmed the gunmen were still holed up in Pathankot air base in Punjab state, a day after the pre-dawn raid in which four attackers and six Indian military personnel were killed.

Indian leaders had already praised the armed forces for their heroism in Saturday's 15-hour shootout, with Prime Minister Narendra Modi saying they did not let the "enemies of humanity" who attacked the base succeed.

But that appeared premature on Sunday, as the operation resumed to secure the air base that sprawls across an estimated 14 square km and lies just 25 km (16 miles) from the border with historic rival Pakistan.

Outside the base, rumours had circulated all morning that more gunmen were still active after Home Minister Rajnath Singh had announced on Saturday that five terrorists had been "neutralised". The official body count was only four, however.

10 people are killed in an audacious pre-dawn assault on an air force base, officials said on Sunday after a 15-hour gunbattle. In the photo, an Indian security personnel stands guard next to a barricade outside the Indian Air Force (IAF) base at Pathankot in Punjab, India, January 2, 2016. Photo: Reuters

One of the Indian security men killed in the attack was Subedar Fateh Singh, who won gold and silver medals in the first Commonwealth Shooting Championships held in 1995, the National Rifle Association of India said.

Nuclear neighbours

The attack by gunmen disguised as soldiers came a week after Modi made an unscheduled visit to Pakistani counterpart Nawaz Sharif in an effort to revive talks between the nuclear-armed neighbours.

Officials said the attack bore the hallmarks of previous suspected assaults by Pakistan-based militant groups, underscoring the fragility of recent efforts to revive bilateral talks between the often uneasy neighbours.

There was no immediate claim of responsibility.

Pakistan condemned the attack and said it wanted to continue to build on the goodwill created by the impromptu meeting between Modi and Sharif last month.

At least two security personnel were wounded in a blast on Sunday, a police official in Pathankot said, as troops scoured the base. One later died, according to reports that could not immediately be confirmed.

The breaching of the base's defences has raised questions about lax security on the international border in Punjab, which is a known route for drug smugglers and is less closely guarded than the disputed frontier running through Kashmir.

Most of the Indian military reported killed had retired from active service and belonged to the Defence Security Corps, a unit that staffed by veterans no longer in active service.

Indian police personnel display a cartridge shell near the Air Force Base in Pathankot on January 2, 2016 during an ongoing attack on the base by suspected militants. Photo: AFP

"The casualties were unacceptably high," said Nitin Gokhale, a defence analyst and journalist who said that intelligence on a possible attack had not been circulated in time to alert the sentries at the base.

Police have said the gunmen had earlier hijacked a police officer's car and driven it to the base. It took 12 hours for information on the hijacking to be circulated, according to news reports, allowing the attackers to keep the initiative.

In New Delhi, two trains were delayed early on Sunday amid heightened security concerns after officials received information about a possible bomb threat on a train running between the capital and Lucknow to the southeast, railways spokesman Neeraj Sharma said.

Trains were deemed safe and were running on schedule by mid-morning, Sharma said.