The current terror threat level has been classed severe - one level lower than the highest "critical" - since 14 August 2006.

BBC: NEWS | UK | Two car bombs found in West End

The terror threat level on the UK Home Office website remains unchanged at "substantial, " which is the third highest of five levels.

CNN: London's Olympic security headache

As we've been reporting, in the wake of today's bombings in London, US officials have raised the terror alert level for mass transit systems.

NPR: New York, Los Angeles Step Up Security

France increased its domestic terror threat level after French forces went into action in Mali on 11 January to push back militants who had captured Timbuktu and other parts of northern Mali.

BBC: A French soldier patrols a street in Paris, 15 January

Outgoing Homeland Security Undersecretary Asa Hutchinson said federal authorities were not ready "to shake up America on this" by raising the nation's terror alert level above its current status of yellow, or elevated.

CNN: Officials: Bin Laden message to al-Zarqawi intercepted

New York has been on "orange" alert, or the second-highest level -- indicating a high risk of terror attack -- since the color-coded warning system was established after the September 11, 2001 attacks.

CNN: New York subway system on alert