Indian troops backed by helicopters searched an air force base Monday after a weekend of fierce fighting with insurgents left seven soldiers dead.

The ongoing operation came as an umbrella group of Pakistani proxy jihadist outfits fighting in Indian-controlled Kashmir, the United Jihad Council, claimed responsibility for the attack in a statement issued to the media.

"The attack on Pathankot air base is actually a message from the Pakistani mujahideen that no single sensitive Indian installation is out of their reach," said spokesman Sayed Saqqat Hussain in the statement, which called on Delhi to grant self-determination to Kashmiri citizens.

Earlier Monday, a senior Indian security officer said a fifth attacker had been killed, in addition to four gunmen killed earlier at the Pathankot base in the northern state of Punjab near the border with Pakistan.

"We have been able to eliminate the fifth terrorist. The combing and search operations still continue," the officer from the National Security Guard (NSG), a special forces unit, told journalists on condition of anonymity.

He did not say what day the fifth attacker died.

The base was hit in a dawn raid Saturday that triggered a 14-hour gunbattle and there was more firing Sunday.

It was not clear Monday whether any surviving attackers remained inside the base but troops were still searching.

Security officials said they were focusing on a two-storey building that contained living quarters for families on the base where the militants had previously holed up.

"We are moving step by step to sanitise the area and it's too early to say when the operation will be over," said another military official who asked not to be named.

The NSG officer added that all assets at the base "including personnel and their families have been secured and are now safe".

"As highlighted earlier, because of the magnitude of the air base, the operation will continue till we are able to fully render it safe," he added.

- Landmark visit by Indian PM -

The attack -- a rare targeting of an Indian military installation outside disputed Kashmir -- may have been intended to undermine improving relations with Pakistan after a landmark visit to the neighbouring country by Indian Prime Minister Narendra Modi last month.

Finance Minister Arun Jaitley refused to comment on the impact of the attack on Modi's bold peace initiative, after the premier's surprise visit to meet his counterpart in the Pakistani city of Lahore.

"The intelligence input really helped, which is why we could promptly stop them at a distance to contain and neutralise them at a distance from our strategic assets," Jaitley told state broadcaster Doordarshan without giving details of its source.

"The casualties of the security personnel are very unfortunate... the aim was to neutralise them or catch them without loss of assets."

Before Monday's claim of responsibility, security officials had suspected the gunmen belonged to the Pakistan-based Jaish-e-Mohammed, the group that staged the 2001 attack on the Indian parliament which brought the two countries to the brink of war. It is not part of the United Jihad Council.

The United Jihad Council is currently headed by Syed Salahudin of jihadist group Hizb-ul-Mujahideen.

An AFP reporter at the scene said sporadic gunshots could be heard inside the air base Monday as army helicopters surveyed the site, but the reason for the shots was unclear.

Pathankot houses dozens of jet fighters and is located just 50 kilometres (30 miles) from the Pakistan border.

Seven soldiers including a lieutenant-colonel in the NSG were killed and 20 injured in the assault.

Such attacks are relatively rare outside the volatile disputed region of Kashmir.

But in July three gunmen said to be Pakistan-based Lashkar-e-Taiba militants killed seven people including four police in an attack in the Sikh-majority state of Punjab.

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NIPPON SHEET GLASS