Some of the gunmen involved in the Mumbai attacks are believed to be British-born Pakistanis, it was reported.
Indian news channel NDTV reported that "British citizens of Pakistani origin" were among the attackers.
A Foreign Office spokeswoman said: "We have seen the media reports but we are not aware of anything giving any credence to those reports at the moment."
Meanwhile, Foreign Secretary David Miliband has expressed sympathy with the family of Andreas Liveras, the one Briton confirmed dead after terrorist attacks in Mumbai.
Mr Miliband said: "This is a callous, inhuman and indiscriminate attack on people of all races and all religions.
"This attack in Mumbai is an attack on all of us because democracy in India is vibrant and because Mumbai is one of the world's most diverse cities.
"The most terrible thing is that we do have one confirmed British fatality.
"Obviously our hearts go out to the family of the victim and we are determined to do all we can to support those who are currently in hospital."
Prime Minister Gordon Brown said the terrorist attacks were met by "shock and outrage" around the world and pledged all possible UK support for the Indian authorities in dealing with it.
Mr Brown spoke on Thursday after visiting staff at a Foreign Office emergency response centre, which he said had already taken more than 800 calls.
