"We caught them from Mahavir parking area," Joint Commissioner of Police (Special Cell) PN Agarwal said.
The arrest came nine days ahead of the Independence Day celebrations in the national capital.
"We had intelligence inputs about the movement of these militants and we tracked them," the officer said.
The arrest came hours after Union Home Ministry made public intelligence inputs about LeT planning terror attack in three cities -- Delhi, Hyderabad and Kolkata -- ahead of August 15.
The official said two AK-47 rifles, about 100 catridges and two grenades were also recovered from the militants, who were in their early 30s.
Asked about their nationality, the official said they appeared to be Indians.
Following intelligence inputs about terror strikes, the Delhi Police has deployed hundreds of policemen and paramilitary personnel across the city.
Security agencies are constantly reviewing arrangements at the Red Fort, where Prime Minister Manmohan Singh will unfurl the tricolour.
Specialised units like Quick Reaction Teams, Special Weapons and Tactics (SWAT) and Vajra (of the Rapid Action force) are being deployed, an official said.