British police are reviewing security plans for Sunday's London Marathon, the next major international marathon, because of the deadly bombs that hit the race in Boston on Monday.

The London Marathon is a hugely popular race. Last year, some 37,500 athletes competed, with many more watching the springtime event.

London has long been considered a top target for international terrorists. 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 at least two people, and injuring 22 others, race organizers and police said.

A London Metropolitan Police spokesman confirmed Monday that police here are working with marathon officials to review security plans for Sunday's race, with an eye toward establishing a larger security presence. The spokesman spoke on condition of anonymity because he was not authorized to go on the record.

The London race's chief executive, Nick Bitel, 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."