Britain has warned its nationals that they should be careful while visiting Goa and the four major Indian metropolitan cities, including Delhi and Mumbai, which could be terror attack targets.

"Future attacks may target public places frequented by Westerners and expatriates, including the major metropolitan centres (Delhi, Kolkata, Chennai, Mumbai) and tourist areas such as Goa," says a travel advisory on the British government's foreign commonwealth office (FCO) website, which was updated November 11.