The US has warned of possible terror attacks in India in the coming days.
Security is always tightened on the eve of Independence Day
The US embassy in India said they could take place in Delhi and Mumbai (Bombay) ahead of India's Independence Day celebrations on Tuesday.
The embassy said it had information that foreign terrorists were planning to carry out bomb attacks around the two cities.
Mumbai's police chief says he is increasing security because the city is facing attacks.
AN Roy was speaking one month after more than 180 people in Mumbai were killed by a series of bomb attacks on commuter trains.
"We do get intelligence inputs that some more attempts are likely to be made at some time," he told the BBC.
American citizens in Delhi are being advised by the embassy to "maintain a low profile, be alert and attentive to their surroundings".
The advisory warned that terrorists, "possibly including members of al-Qaeda" were likely to target "major airports, key central Indian government offices, and major gathering places such as hotels and markets".
India says it has no information of the US warning, which comes exactly a month after more than 180 people were killed in Mumbai in a series of bomb blasts on commuter trains.
"We have not received any formal communication from the US authorities," India's junior foreign minister, Anand Sharma, told journalists in Delhi.
He added: "Our security and intelligence agencies are fully prepared to meet any threat. We are aware that India is a target of terrorist groups."
The senior official in the home ministry, Vinod Kumar Duggal played down the US alert: "It is normal for missions to issue advisories when they have any information
"It's a very innocuous advisory... to their own staff."
Extra security measures have already been put in place at Indian airports and other public places.
There are also reports that army troops are being deployed at some of India's atomic plants.