British police receives coded bomb threat for London from Irish republicans on eve of historic trio by Queen Elizabth II to Ireland

British police received a coded bomb threat for London from Irish republicans Monday, on the eve of a historic trip by Queen Elizabeth II to Ireland and just a week before US President Barack Obama is due to visit the British capital.

Police sealed off roads near Buckingham Palace and carried out a controlled explosion after the warning, as a Scotland Yard spokesman was stressing that the threat is not specific in relation to location and time. "We believe the threat is in connection with dissident Irish republican terrorism," the spokesman told AFP.

There has been a recent upsurge in dissident republican violence in Northern Ireland, with a policeman killed by a bomb in April, but Scotland Yard said there had been no change in the official threat level. "The threat level from Irish-related terrorism has not increased and remains at substantial, meaning that an attack is a strong possibility. The threat level was raised in September 2010 from moderate to substantial," a statement said. The threat level was lower than that from international terrorism, which remains at "severe", it said.

The queen arrives in Ireland on Tuesday for a four-day trip, with reconciliation the theme in the first state visit by a British monarch since the republic gained independence in 1922. The visit will be surrounded by a massive security operation amid threats from dissident republicans to the peace established in British-ruled Northern Ireland as a result of the 1998 Good Friday accord.