Extra police was deployed at various transport hubs in the city and all police leave cancelled after intelligence was received that terrorist could be planning fresh attacks, British media reports today said quoting security officials.
Security was beefed up at London`s Heathrow airport and the Luton airport and at all major railway stations as reports said that terrorist could be preparing to target transport hubs in the city, The Daily Telegraph reported.
The British police have kept the overall threat at the second highest level "severe" which means that an attack is highly likely.
Sky news quoting Scotland Yard officials said members of the emergency service have been briefed about how to respond to Mumbai style-attack.
A security source said there was no "imminent" threat and the overall threat level had not changed but there was activity from one of a "handful" of extremist cells that cause concern at any time, leading to an adjustment in policing levels.
He said intelligence intercepts were not clear whether the terrorist were planning suicide bomb attacks of Mumbai-style shootings or a combination of both.
"We will use a range of covert and overt tactics to deal with the threat," he said.
The British police have been on high alert since September after intelligence agencies received informations about simultaneous Mumbai-style attacks on cities in France, Germany and the UK.
The plan was in advance stage and the plotters had been tracked by spy agencies.
There have been two serious terrorist plots in the last few weeks that have been linked to Britain. Security agencies recently arrested 10 persons of Pakistani and Bangladeshi origin who have been charged with plotting terror acts.
On December 11, a suicide bomber blew himself up in Stockholm, Sweden while heading towards the central train station.
In Denmark last week, police arrested three men with a submachine gun, silencer and ammunition who were allegedly planning a Mumbai-style shooting spree.
Both plots had links to Britain ? the Stockholm bomber, Taimour Abdulwahab al-Abdaly, had been living in Luton, while the alleged Danish terrorist cell had links to a network in Derby, the Daily Telegraph reported.