Pakistan Prime Minister Nawaz Sharif spoke to Indian Prime Minister Narendra Modi on Tuesday and assured prompt action in the investigation in the Pathankot terror attack.

"PM Modi emphasized the need for Pakistan to take firm and immediate action against the organisations and individuals responsible for or linked to the Pathankot terrorist attack," the statement shared by Ministry of External Affairs spokesperson Vikas Swarup on Twitter said. 

Sharif's call to Modi comes after the Indian PM faced strong criticism from the Opposition and other parties as the attack came days after his 'surprise' visit to Pakistan on 25 December. The stop-over had indicated improving ties between India and Pakistan.

Some reports suggest that the militants had links with the Pakistani Army and the Inter-Services Intelligence (ISI) -- Pakistan's spy agency. Defence Minister Manohar Parrikar said during a press conference on Tuesday that there were indications that some of the equipment used by the terrorists were made in Pakistan. 

On Monday, US state department Spokesman John Kirby said that it was expected that Pakistan will crack down on terrorists behind the Pathankot attack.

"We have been clear with the highest levels of the government of Pakistan that it must continue to target all militant groups," Kirby said.

Pakistan had condemned the attack and said it was working on leads provided by the Indian government.

"In line with Pakistan's commitment to effectively counter and eradicate terrorism, the Government is in touch with the Indian government and is working on the leads provided by it," the Pakistan government had said in a statement on Monday.

The anti-terror operation at the Pathankot Air Force base ended on Tuesday, according to reports, four days after terrorists stormed the station, killing six Indian security officers. Another officer, National Security Guard Lieutenant Colonel Niranjan Kumar, was killed in a grenade explosion during combing operations.

Six terrorists were neutralised, Parrikar said.