Soldiers were on 24-hour guard at the Taj Mahal after officials received a letter threatening to blow up the monument, officials said Friday.
Authorities were investigating a handwritten letter received Thursday — purportedly sent by an Al Qaeda supporter — that said the terrorist group planned blasts at the 17th century monument, which drew nearly 2.5 million tourists last year.
"Police are verifying the source of the letter," said Ashok Kumar, a senior government official in Uttar Pradesh state where the Taj Mahal is located. "The letter could be false but we cannot afford to be complacent. We are not taking any chances and have enhanced security at the Taj."
At least 100 additional paramilitary soldiers with automatic weapons have been posted around the Taj Mahal complex, authorities said.
The state government has asked the federal civil aviation authorities and India's air force to declare a no-fly zone within a 2.5-mile radius of the Taj Mahal, said N. C. Bajpei, Uttar Pradesh's highest official.
Tourists have been warned not to carry any liquids, including bottles of mineral water, to the fabled white marble structure located in the city of Agra, 130 miles from the Indian capital, New Delhi. Sandbag bunkers also have been set up outside the towering entrance gates, Kumar said.
The majestic domed monument was built by the Mogul Emperor Shah Jehan between 1632 and 1654 for his favorite wife, Mumtaz Mahal. It houses their graves and a mosque, as well as several graves of lesser Mogul royalty.
India deployed tens of thousands of police to patrol major cities and posted sharpshooters on rooftops Tuesday as the country marked 59 years of independence under a terror alert. The celebrations came a month after the train bombings in Bombay killed 207 people.