The security forces have launched a fresh counter-attack as two more terrorists are still holed up inside the Indian Air Force (IAF) base in Pathankot, Punjab, according to reports.

"There are 2 more terrorists inside Indian Air force Base in Pathankot, operation continuing," DIG (Border) Kunwar Vijay Pratap Singh told ANI

At least four terrorists were gunned down on Saturday in almost 15-hour long fierce gun-battle with the security forces at the base.

However, fresh counter-attack resumed on Sunday afternoon after one National Security Guards (NSG) Lieutenant Colonel was killed and three jawans were injured in fresh explosions at the base during search operation. Reports of fresh rounds of firing also emerged later on Sunday.

NSG Lt Colonel Niranjan E Kumar, who was injured in the blast during search operations on Sunday morning, succumbed to his injuries later.

Another NSG jawan was injured in a second explosion that took place at around noon.

Live Updates:

4:04 pm: At the moment our understanding is four terrorists have been killed & two are being engaged now: Punjab Deputy Chief Minister Sukhbir Singh Badal

4 pm: Punjab Police will act as the second line of defence whereas BSF will be first line of defence: Badal

3:56 pm: A commando battalion will be established in Pathankot district. They should increase deployment in this fencing area, for this is the second/third time such incident has happened in Punjab: Badal

3:05 pm: Firing is underway at the base.

2:56 pm: One terrorist has been cornered by security forces.

2:49 pm: Counter attack underway at the IAF base.

2:46 pm:

1:40 pm: Two more terrorists are inside the Air Force base. Counter operation is underway at the site.

The security forces, including Army, the Punjab Police, NSG, Indian Air Force and paramilitary forces, are simultaneously carrying out an extensive search operation at other parts of the base and areas surrounding it.

Delhi on high alert

Delhi has been put on high alert after the Pathankot terror attack and security at sensitive locations has been beefed up. 

The security agencies have become more vigilant following a bomb scare on Delhi-Lucknow Shatabdi Express. Although nothing was found during the extensive search operation at the Delhi railway station and the train, security at other parts has been increased.

"We have deployed bomb disposal squad and intensified the general checking... But there is no need to panic," deputy commissioner of police, Railways, Dumbere Millind Mahadeo told IANS.

Saturday attack in Pathankot

A group of four terrorists had attacked the Air Force base at around 3:30 am on Saturday, leading to a fierce gunfight with the security forces, including NSG commandos, the IAF's Garud commandos, Army commandos, and Punjab Police and SWAT commandos.

The gun-battle halted at around 9 am on Saturday, but fresh firing and grenade explosions were heard again at around 11:30 am, leading to further gunfight. The counter-attack lasted for nearly 15 hours, during which the security personnel killed all four terrorists, while three jawans were also martyred, IANS reported.

At least nine other jawans were reported injured in the gun-battle, of which three succumbed on Sunday.

The IAF had issued a statement in Delhi saying they had received inputs about a possible terror attack on military installations and security forces were rushed to Pathankot on Friday evening to thwart any such attempt. 

The statement said terrorists had planned to destroy "valuable assets". "The terrorists were contained in one area of the air force station. They could not reach near the technical area of the air force station where IAF aircraft and other assets are located," a Punjab Police officer stationed near the IAF station told IANS.

Intelligence agencies suspect that the militants belonged to Pakistan-based Jaish-e-Mohammed (JeM) terror group, headed by Maulana Masood Azhar, who was freed during the Kandahar hijack in December 1999.

The terrorists are suspected to have crossed the border from Pakistan to enter Pathankot on 30-31 December.

The National Investigation Agency (NIA) has been handed over the probe of the Pathankot terror attack. An NIA team has arrived in Pathankot on Sunday.