An unprecedented security cover has been thrown around the capital on the eve of the Republic Day even as police foiled a major terrorist bid to subvert the national event by arresting a Lashkar-e-Toiba operative with explosives.

The Pakistani-trained militant, identified as Iftikhar Alam, was arrested from a bus stand near the metro station in Seelampur locality of North-East Delhi on Thursday evening.

Around 2.5 kg of RDX, two detonators and a timer have been recovered from his possession.

"He was here to deliver the explosives to someone for carrying out strikes on the occasion of Republic Day," Joint Commissioner of Police (Special Cell) Karnal Singh said.

A resident of Nalanda, Alam arrived in Delhi from Patna on Thursday morning by the Sampoorna Kranti Express.

However, his contact in Delhi is yet to be identified, leaving the security personnel on tenterhooks on the eve of the R-Day to be attended by President A P J Abdul Kalam, Prime Minister Manmohan Singh, visiting Russian President Vladimir Putin and the country's political and military top brass.

In another alarming incident, police arrested a man from the Old Delhi Railway station with a live smoke grenade.

Mohd Hussain Sheikh, hailing from West Bengal, was nabbed during a routine checking and booked under the stringent Explosives Substances Act.

What is worrying the entire security establishment is the information revealed by Alam that the unidentified person who was to collect the explosives from him had conducted a recce of several locations including vital installations in the capital for carrying out attacks.