LONDON - British police are reviewing security plans for Sunday's London Marathon, the next major international marathon, because of the bombs that killed two people at the race in Boston. But there is no known specific or credible threat against the hugely popular British race at the moment, a security official said Monday.

Police already were preparing a major security operation for Wednesday's ceremonial funeral for former Prime Minister Margaret Thatcher, an event at St. Paul's Cathedral that will be attended by Queen Elizabeth II and many dignitaries. The plans call for a procession through the streets of London, with Thatcher's flag-draped coffin to be carried on a horse-drawn carriage.

The funeral's security plans are expected to be reviewed in light of the Boston bombings.

London has long been considered a top target for international terrorists, with the government saying the threat level is "substantial." In 2005, a series of suicide attacks on the public transport system in the British capital killed 52 people. London and mainland Britain also face a moderate threat from Northern Ireland-related terrorism, according to the government.

Two bombs exploded near the finish of the Boston Marathon on Monday, killing two people and wounding more than 80 others, race organizers and police said. The situation sparked alarm bells in Britain, where a massive security operation was put in place last summer to protect the successful London Olympics.

Last year, some 37,500 athletes competed in the London Marathon, with many more watching the springtime event.

Chief Superintendent Julia Pendry, police commander for the London race, said Monday that "a security plan is in place for the London Marathon. We will be reviewing security arrangements in partnership with (the) London Marathon."

A police spokesman who spoke on condition of anonymity because he was not authorized to go on the record said the security presence may be increased.

A security official, speaking on condition of anonymity because he was not authorized to speak publicly about the matter, said there are no credible or specific threats against the London Marathon.

The London race's chief executive, Nick Bitel, said marathon officials contacted the police to discuss security plans "as soon as we heard the news" about Boston. He expressed shock and sadness about the situation in Boston, saying "it is a very sad day for athletics and for our friends in marathon running."