At least one helicopter could be seen later in the day firing at an area inside the Pathankot air force base. Shots could also be heard from inside the base. No other details were available and phone calls to Defense Ministry and air force officials went unanswered.
Air force spokeswoman Rochelle D'Silva said earlier Saturday that at least four gunmen entered the living quarters of the base, about 430 kilometers (267 miles) north of New Delhi, but were unable to penetrate the area with fighter helicopters and other equipment.
Press Trust of India news agency quoted police as saying that four attackers were killed following an hourslong gunbattle, and that police started an operation to clear a wider area of other possible intruders.
Pathankot, in Punjab state, is on the highway that connects India's insurgency-wracked Jammu and Kashmir state with the rest of the country. It's also very close to India's border with rival Pakistan.
Police were investigating whether the militants came from the Indian portion of Kashmir or from Pakistan. Rebels routinely stage attacks in Indian-held Kashmir, where they've been fighting since 1989 for an independent Kashmir or its merger with Pakistan.
Saturday's attack comes just a week after India's Prime Minister Narendra Modi made an unannounced visit to Pakistan to meet with Prime Minister Nawaz Sharif.
The visit was seen as a potential sign of thawing relations between the two nuclear-armed neighbors. The two heads of government also had an unscheduled meeting at the Paris climate change talks.
India accuses Pakistan of arming and training Kashmir's insurgents, a charge Islamabad denies. More than 68,000 people have been killed in the violence in the Indian portion of Kashmir.
Indian Home Minister Rajnath Singh told reporters Saturday that India wants peace with Pakistan, but "if there is any kind of terror attack on India, we will give it a fitting reply."
In July, gunmen staged a similar attack at a police station and a moving bus near Gurdaspur, a border town in India's Punjab state. The three attackers then killed four policemen and three civilians before being shot dead by security forces.
Related story
4 gunmen, 2 troops dead in attack on Indian air base
