New Delhi: January 25, 2010 -  Amid threats of hijack and air-borne suicide attacks, the national capital on Monday turned into a citadel on the eve of the 61st Republic Day.

Elite commandos of the National Security Guards (NSG), central paramilitary forces, sharpshooters and snipers of the Delhi Police were keeping a tight vigil between Vijay Chowk and the historic Red Fort — the eight km stretch through which the parade would pass.

Besides commandos and sharpshooters, around 18,000 security personnel were working in close coordination with the intelligence agencies and armed forces to throw an impregnable security cover.

Air Force on high alert

The Indian Air Force has been asked to remain on high alert. Its helicopters will patrol the sky to counter possible threats from banned terrorist organisation Lashkar-e-Taiba (LeT).

Anti-aircraft guns too have been mounted at undisclosed locations. The airspace for commercial flights will be closed while the parade passes down Rajpath. A large number of closed circuit television cameras have been installed for electronic surveillance of the entire parade area.

"We have placed multi-layered security and are leaving no stone unturned to ensure a peaceful Republic Day," a police officer said.

Vehicular movement on all roads leading to India Gate in the heart of the city will be regulated. The vehicles will not be allowed to enter the parade route and Metro services in the vicinity will be curtailed.

Impact on Delhi Metro

"There will be restrictions on Metro services till 12 p.m. on Tuesday. Trains from Dwarka will terminate at Barakhamba while those from Jahangirpuri will terminate at Rajiv Chowk. From Anand Vihar, the trains will come till Yamuna Banks while those from Noida will terminate at Indraprashta," an official said.

Delhi's borders will be sealed from 11 p.m. on Monday to 12 p.m. on Tuesday.