Police officers are being added to transportation hubs around London on heightened fears of terrorist attacks, local media reported on Thursday.
Time off for transportation officers was canceled this week and extra officers have been deployed across London and outlying areas, sources said.
The change in policing levels was due to activity at one of a "handful" of extremist cells, according to the U.K.'s Telegraph. "Intelligence chatter" suggested that transportation centers in London could be a target.
"The assessment of the threat to transport hubs has been revised," a source told the Telegraph. "The view is that there is a greater risk than before, so steps are being taken as a precaution."
The U.K. Home Office told NBC News they could not confirm or deny the report because "they they don't comment on specific security matters."
In addition to the added police presence, emergency workers have recently been briefed on how to respond to a Mumbai-style attack on the capital, according to Sky News. The 2008 Mumbai attacks included more than 10 coordinated shooting and bombing raids across India's largest city.
The threat level for international terrorism in the U.K. has remained at "severe" —the second-highest level — since January 2009, a source at the U.K.'s Home office reiterated to NBC News, and there has been no change. The highest threat level is "critical."
Two recent terrorist plots in Europe have been linked to Britain.
Three men held in an alleged plot to attack a newspaper office in Copenhagen, Denmark, on Dec. 29 purportedly had links to a terror cell in Derby, England. The paper had published caricatures of the Prophet Muhammad in 2005.
Taimour Abdulwahab al-Abdaly, a suicide bomber who had been living in England, blew himself up in downtown Stockholm, Sweden, on Dec. 11.
