The Pathankot attack and terror threats have raised concerns ahead of the Republic Day celebrations as French President Francois Hollande will be the chief guest at the parade. It is believed that security during the event will be as tight as it was during US President Barack Obama's visit last year.

"Given the cases of some Indians having joined IS and the growing instances of our youth getting radicalized by its online propaganda, with some being prevented from leaving the country to join the outfit, one cannot rule out the threat of a lone wolf attack here. This threat may only become more real ahead of or during Hollande's upcoming visit," The Times of India quoted an officer as saying.

The terror threats are a matter of grave concern as Hollande's visit to India comes almost two months after Isis-led Paris attacks in which at least 130 people were killed. In retaliation, France had carried out airstrikes against the Islamic State in Syria.

Also, recent reports suggested that two operatives of Jaish-e-Muhammed have sneaked into Delhi with intentions to carry out "high-profile attacks" and create "hostage crisis" in the national capital.

There were other reports suggesting that one of the militants who entered Delhi has moved towards the Delhi airport. In the wake of possible terror threat, the airport and all airlines flying out of Delhi have been asked to tighten security, The Economic Times reported.

The alert was sounded just a day after a group of six militants attacked Indian Air Force base in Pathankot, Punjab. All six terrorists were reportedly killed and seven security personnel lost their lives during the three-day confrontation between the militants and security forces at the base.

"We have to take into account all these factors and accordingly tailor our security arrangements for his visit," TOI quoted the officer as saying. He said there is a possibility that this year's security arrangements will be similar to last year's when Obama was the chief guest at 66th Republic Day celebrations.

The security agencies had deployed over 1,000 NSG snipers on high-rise buildings within a two-km radius of Rajpath and at least 44,000 security personnel from Delhi Police and paramilitary forces were put in place across Delhi for 2015 Republic Day celebrations attended by Obama, IANS reported.

More than 14,000 CCTV cameras were installed across the national capital, particularly on the routes taken by Obama's cavalcade. A seven-layer security ring guarded the bullet proof enclosure where Obama, Prime Minister Narendra Modi and Indian President Pranab Mukherjee were seated during the parade.