LONDON, (Reuters) – Britain raised its international  terrorism threat level to ‘severe’ — its second highest level  of terror alert — from ‘substantial’ yesterday, Home Secretary  (interior minister) Alan Johnson said.

“The Joint Terrorism Analysis Centre has today raised the  threat to the UK from international terrorism from substantial  to severe. This means that a terrorist attack is highly likely,  but I should stress that there is no intelligence to suggest  than an attack is imminent,” he said in a statement.

“JTAC keeps the threat level under constant review and makes  its judgments based on a broad range of factors, including the  intent and capabilities of international terrorist groups in the  UK and overseas,” the statement said.

Britain, a close U.S. ally, hosts an international  conference on Afghanistan on Jan. 28 that London says may set a  timetable for transferring responsibility for some areas to  Afghan control.

Those present will include Afghan President Hamid Karzai,  U.N. Secretary-General Ban Ki-moon, NATO Secretary-General  Anders Fogh Rasmussen, U.S. Secretary of State Hillary Clinton  and foreign ministers of Afghanistan’s other main partners.

The threat level was last changed on July 20, 2009 when it  was lowered to substantial from severe. It had been lowered to  severe on July 4, 2007 from critical, the highest level, which  had been declared on June 30, 2007.