NEW DELHI: The day before a deadly assault on an air base in Pathankot, a police officer returning from a temple was abducted by a group of heavily armed men speaking Urdu, he said on Tuesday. 'The minute I saw them I realised that they were terrorists,' Police Superintendent Salwinder Singh told media. 'One of the gunmen snatched my phone and made calls to Pakistan,' Singh said. Urdu, widely spoken in Pakistan, can be mostly understood by Hindi speakers. The colleague Singh called after he was freed treated it as an armed robbery, one in a string of security lapses preceding the Jan. 2 assault on the Pathankot air base that killed 7 Indian security personnel and injured 22. Mobile phone tower records indicate the perpetrators made calls from Singh's phone from inside the air base by mid-afternoon on Jan. 1, according to the Indian Express, some 12 hours before the government said it had detected them through aerial surveillance. Operations to secure the vast air base in Punjab stretched into a fourth day on Tuesday, as forces cleared the grounds and hundreds of police combed a forested area surrounding the base for possible collaborators. Indian forces had killed five militants involved in the attack, but it was unclear whether more remained at large in the sprawling facility 25 km (16 miles) from the Pakistani border. 'We cannot inform whether there are more militants or not,' said Manish Mehta, an Indian army spokesman. The apparently well-planned assault on a strategic military target has cast a shadow over efforts to improve relations between India and Pakistan. Talks between their foreign secretaries are due on Jan. 15. On Monday, the United Jihad Council, an alliance of pro-Pakistan militant groups based in the Pakistani-administered part of the divided Kashmir region, claimed responsibility for the assault, saying in a statement that 'no sensitive installation of India is out of our reach'. India is mulling whether or not to go ahead with the talks with Pakistan, a government official said on Monday, and would reach a decision after operations at the air base are concluded. Pakistan has strongly condemned the incident. Its foreign ministry said the government was committed to a 'sustained dialogue process' and that India had shared leads on the assault. It remains unclear exactly how the attackers infiltrated the fortified and guarded base, which has a 24-km (15-mile) perimeter surrounded by a 3-metre (10-foot) concrete wall topped with concertina wire. As clearance operations continued, military officials were developing a plan to reinforce the base, a senior air force official in Delhi said, including putting up new fencing and employing more modern security technology. 'Security at every defence establishment will be evaluated,' the official said.