A youth was arrested on Sunday while allegedly trying to enter the high security Tihar jail complex, police said.
Ajaz Ansari was intercepted by the ITBP personnel on duty at around 10:30 am while he was moving towards Gate No 6 in a suspicious manner.
The 20-year-old youth was immediately taken into custody and questioned by the security personnel at the prison and later handed over to Delhi Police.
After initial interrogation, police suspect that he was mentally deranged but they are not taking any chances in view of the threat perception prevailing in the capital ahead of the Independence Day.
A mobile phone and a diary have been seized from the possession of the youth, a resident of Delhi who belongs to Bihar.
The national capital is in a state of high alert after specific intelligence inputs warned of terrorist attacks to subvert Independence Day celebrations.
Police said they have received inputs that indicated renewed determination of various terrorist outfits to target prominent political leaders and symbols of national importance.
Police have put in place an unprecedented 'ground-to-air' security cover in the Capital and deployed over 10,000 police personnel and elite commandoes of National Security Guards and ITBP to ensure smooth conduct of the national event.