Security forces continued search and combing operation inside the Pathankot airbase on Tuesday — the fourth day after the attack on the frontline Air Force Station (AFS) by terrorists.

The operation was stepped up on Tuesday, an Air Force official told IANS. Firing could be heard from inside during Monday night and early Tuesday.

A military official said a fifth terrorist was killed on the third day of the siege and at least one attacker remained in the complex, as troops worked to secure the sprawling compound.

What we know so far and the unanswered questions:

› January 1 (Friday) Early morning (around 3 am): SP Salwinder Singh and his cook Madan Gopal alert local police about terrorists who abducted them Their claims were not given credence for hours; crucial time was lost. Afternoon: Centre issues alert about terrorists; by now more or less certain their location was Pathankot. NSA convenes meeting with senior officials; NSG dispatched to Pathankot Why no detailed combing of the region done, despite several military, BSF and Punjab police units available close by? › January 2 (Saturday) Early morning (3.30 am): Terrorists spotted; Centre claims they were contained in forested area Evening: Four terrorists killed; Home Minister claims operations over Who briefed Home Minister, and why was haste shown in declaring operation a success? › January 3 (Sunday) Morning (10 am): NSG's Lt Col Niranjan killed, five others injured while inspecting a terrorist's body 12.20 pm: Firing starts from two different locations, security forces realise more terrorists are alive Why was no protocol in place to avoid such casualties? Why was there no careful combing and clearing of the area?

Latest updates:

Tuesday (January 5)

6.55 pm: It is for NIA to comment if SP Salwinder Singh is under the scanner or not: Punjab DGP.

6.55 pm: Received the info at 3.23 a.m. from SP, followed up action immediate, ADGP (L & O) went to the base at 7 a.m., other agencies were alerted.

6.50 pm: No time lost in corroborating SP's account, all action simultaneous: Punjab DGP.

6.48 pm: Punjab DGP: All necessary actions were taken by us. How was NSG deployed before the attack if not because of swift action?

5.00 pm: Specific and actionable information regarding Pathankot attack has been provided to Pakistan, says PMO. - PTI

4.25 pm: BSF has started probing how did the attackers enter India, won't comment on Punjab Police or government. : Parrikar

4.24 pm: NSG was called because threat of civilian casualties was there, Parrikar says.

4.23 pm: Security was adequate but yes, some gaps have been found, says Defence Minister Manohar Parrikar.

4.22 pm: Army cannot be used to do civil duty, guard roads, area complicated: Parrikar.

4.20 pm: They sneaked in with 50 kgs of bullets, under barrel grenades. Some of the material was from Pakistan. 1900 acre is the total area : Parrikar.

4.19 pm: All deceased will be declared as martyrs; state government has also announced compensation, Parrikar says.

4.18 pm: Only the Garud Commando's death was an operational loss: Parrikar.

4.17 pm: Operation done without compromising any asset, strategic or otherwise, Parrikar says.

4.15 pm: Operation done without compromising any asset, strategic or otherwise, says Manohar Parrikar.

3.15 pm: Officers say all terrorists dead, unexploded blinds (grenades or shells) left, defusing causing intermittent explosion heard at the IAF base.

3.00 pm: Loud explosion heard from inside the air base. Combing operation underway. - ANI

2.45 pm: Defence Minister along with the chiefs of Army and IAF to address a joint press conference shortly, formal announcement of Operation closure likely.

1:42 p.m.: NIA registers 3 cases related to the attack.

1:25 p.m.: Abducted cop recounts moments before the attack

Gurdaspur SP Salwinder Singh, whose vehicle was forcibly taken away by heavily-armed militants, on Tuesday, said he was blindfolded and the terrorists took two of his three mobiles and fled with his vehicle. More...

11:37 a.m.: Pathankot Attack was not only a terror attack but an attack on humanity. It was an attack on India, says Congress leader Anand Sharma

11:00 a.m.: The Shiv Sena today said it had warned Prime Minister Narendra Modi not to trust Pakistan and that time has now come for him to focus on India rather than trying to unite the world. >Read more

10:44 a.m: Defence Minister Manohar Parrikar along with Air Force Chief Air Chief Marshal Arup Raha and Army Chief General Dalbir Singh Suhag will visit the Pathankot Air Base this afternoon to get a first hand assessment of the ground situation.

10:06 a.m.: Pakistan in touch with India, pursuing ‘leads’

Pakistan Foreign Ministry said it was “working on the leads” provided by the Indian government, and called for a commitment to a “sustained dialogue” process. >More...

10:00 a.m.: Senior officials said the government was weighing its options on whether to go ahead with the Foreign Secretary-level talks scheduled for next week. >More...

9:30 a.m.: NIA team reaches Air Force base.

Monday (January 4)

20.24 p.m: 20 member team of NIA led by an IG ranking officer has been camping at Pathankot since January 2, 2016 to supervise the on-going investigations. - ANI

6.55 p.m.: Intermittent firing heard at Air Force base. - ANI

6.20 p.m.: NIA registers three FIRs in connection with Pathankot Air Force base terror attack.

5.45 p.m.: Next briefing at 10 a.m. on Tuesday, NSG official says.

5.44 p.m.: Combing operations to continue till we can fully render the base safe, says a NSG Official.

5.40 p.m.: The operations are still going on, we eliminated the 5th terrorist, NSG Official says.

5.35 p.m.: Circumference of air base is 24 kilometres, it takes time to comb the area. The process of recovering the last 2 bodies is going on, security forces over there will brief when bodies recovered, Jaitey said.

5.33 p.m.: All consulate officials in Mazar are safe, latest reports say firing still going on. Jawans have given ultimate sacrifice in Pathankot , security forces took prompt action, says Arun Jaitley.

5.24 p.m.:The United Jihad Council, a Pakistan-occupied Kashmir (PoK) based militant conglomerate, has claimed responsibility for the Pathankot attack. UJC is a conglomerate of around 13 militant outfits, including the Lashkar-e-Toiba. >Read more.

5.10 p.m.: Martyrs of Pathankot terror attack were given a final farewell with full military honours in presence of hundreds of people who converged to pay their tributes to the bravehearts. >Read more.

5.00 p.m.: Punjab Chief Minister Parkash Singh Badal meets bereaved families of personnel killed. >Read more.

4.50 p.m.: Government presumes the terrorists smuggled in heavy explosives through the drug-smugglers route in Punjab.

4: 45 p.m.: A building had to be blown up at the Airbase to neutralise the sixth terrorist, he was carrying heavy explosives.

4: 45 p.m.: Two terrorists entered Airbase much before the four men abducted Punjab SP at 1 a.m. on 1st January, says govt official.

4.30 p.m.: Hitting out at the government over the handling of Pathankot terror attack, Congress on Monday said “conflicting” statements on the incident showed “breakdown of institutional mechanism” as Prime Minister Narendra Modi has “concentrated” all powers in his hands. >Read more.

4.05 p.m.: One of the terrorists holed up in the Pathankot air base killed, says top government sources.

3:55 p.m.: Government is “mulling options” regarding holding of Foreign Secretary-level talks with Pakistan in Islamabad on January 15, says PTI quoting top sources.

3:41 p.m.: Kathana Mor, Pathankot where terrorists abandoned Ikagar Singh's vehicle and abducted SP Salvinder Singh and 2 others.

1:03 p.m.: National Security Advisor Ajit Doval’s visit to China for talks with top Chinese leaders has been put off. The visit has been put off due to scheduling problems, Chinese Foreign Ministry official tells PTI. >More...

12:45 p.m.: Major blast in the holed up area of militants at the air base.

From our Correspondent Vijaita Singh:

12:42 p.m.: Six terrorists confirmed dead, combing operation on in 24 sq kms of Pathankot Airbase.

12:39 p.m.: Credible information that attackers received training from a professional armed force in Pakistan: top govt. source

12:34 p.m.: A top govt. source says, 'Pathankot attackers were well-trained, well stocked and more lethal than 26/11 Mumbai attackers'.

12:27 p.m.: “Combings operation continued (on Sunday). This operation is at the completion stage. The operation will continue till the whole air base has been cleared of any intruders,” Air Commodore J. S. Dhamoon, the Air Officer Commanding (AOC) of the Pathankot Air Force Station told the media.

12:22 p.m: Want to compliment agencies participating in this operation, salute personnel who lost their lives or are wounded:Army official

12:22 p.m.: All strategic assets at the air base are safe: NSG.

12:20 p.m.: Terrorists were holed up in a buildng which was living quarters of the IAF personnel.

12:19 p.m: Operations are in progress to clear the building where the terrorists are holed up: Army Official

11:28 a.m.: Mr. Modi meets Defence Minister Manohar Parrikar, NSA Ajit Doval at 7 RCR.

10:10 a.m.: Pathankot terror witness' leads ignored, tortured instead

"I was repeatedly assaulted even as I kept insisting that whatever I had told them was true", says Madan Gopal, one of the three abducted by the terrorists. >More...

9:50 a.m.: The body of National Security Guard commando Lt. Colonel Niranjan E. Kumar (35), who was killed in the anti-terrorist operation, arrives in Bengaluru. >More...

9:00 a.m: Firing erupts again at the IAF base, reinforcements arrive.

Sunday (January 3)

9:00 p.m: Prime Minister Narendra Modi held a meeting with top officials to discuss the Pathankot terror attack.

Soon after returning from his two-day visit to Karnataka, Mr. Modi chaired a meeting of top officials, including National Security Adviser Ajit Doval and Foreign Secretary S. Jaishankar, the PMO said.

8:44 p.m.: NIA to register case tomorrow

The Government has decided to hand over the case to the NIA after taking concurrence from the Punjab government, official sources said.

The mandate of the NIA probe will include entry of the militants into India, killing of a taxi driver Ikagar Singh, kidnapping of Superintendent of Police-rank officer of Punjab Police, who was later released and entry into the IAF campus. >Read more

8:12 p.m: Prime Minister Narendra Modi tweets:

Immediately on landing in Delhi, PM >@narendramodi is chairing a high level meeting with the NSA, Foreign Secretary & other officials. — PMO India (@PMOIndia) >January 3, 2016

7:47 p.m: Fresh explosions followed by intermittent firing erupt at Pathankot Air Force base.

6:32 p.m.: Home Minister Rajnath Singh said terror strikes would have been more severe if there were no intelligence reports.

5:41 p.m.: Operation not over yet: Home Secretary

5:40 p.m.: It's not a lapse at all, when weapons are in use, few security personnel are bound to be injured: Home Secretary.

5:22 p.m: Two terrorists still holed up in IAF base in Pathankot, operation still on: Govt.

3:56 p.m.: We are writing to the Government of India. There is not as much BSF deployment on the Punjab border as compared to the J&K border: Punjab Deputy CM Sukhbir Singh Badal.

3:48 p.m.: One more terrorist confirmed killed: Army

3:30 p.m.: 'JeM militants suspected to be planning attacks in Delhi'

Two Jaish-e-Mohammed militants were suspected to have sneaked into the national capital. The security was today stepped up in the city. >More...

3:00 p.m.: Defence Minister Manohar Parrikar briefs PM Narendra Modi on the situation at the Pathankot air base.

2:30 p.m.:Terrorists holed up

“There is a possibility of two more terrorists being holed up at the Air Force base station,” Kunwar Vijay Partap Singh, DIG Border Range, Punjab Police said

He said the search and combing operation was underway and that further details would be shared later on.

12:15 p.m: Accidental explosion kills Lt. Colonel, toll rises to seven

A senior officer of the National Security Guard (NSG) was killed in an accidental explosion during combing operations at Pathankot air base on Sunday pushing the number of casualties among security forces to seven. The officer has been identified as Lt Col Niranjan.

Defence ministry officials said that it was an Improvised Explosive Device (IED) which went off during combing operations in the morning which killed Lt Col Niranjan and likely injuring few others. >More...