Irish dissident bomb threat shuts down central London

Large parts of central London were closed down Monday after a bomb threat believed to have come from dissident Republican groups in Northern Ireland was received by Scotland Yard, police confirmed.

'We face a real and serious threat from terrorism,' a spokeswoman for the Home Office (Interior Ministry) said.

The coded threat, which triggered a huge security operation, came as Queen Elizabeth II was preparing to visit the Republic of Ireland for a four-day historic visit starting Tuesday.

Also, US President Barack Obama and his wife Michelle are expected on a state visit in London next week.