LONDON (AP) - From London to Sochi to Rio de Janeiro, the deadly bomb attacks on the Boston Marathon raised new concerns on Tuesday over safety at major sports events around the world, including the Olympics and the World Cup.

The twin bombings near the marathon finish line that killed three people and injured 176 brought into sharp focus the security challenges facing next year's Winter Olympics in Sochi, Russia, the 2014 World Cup in Brazil and the 2016 Summer Games in Rio.

"We are very, very concerned," senior International Olympic Committee member Gerhard Heiberg of Norway told The Associated Press. "Security is priority No. 1, no question about it."

More immediate is the security planning for this weekend's London Marathon, which attracts more than 30,000 runners and half a million spectators. Organisers said they were reviewing security for Sunday's race - one of the world's six major marathons - but the event will go ahead as scheduled in a display of unity with Boston.

"The best way for us to react is to push ahead with the marathon on Sunday, to get people on the streets and to celebrate it as we always do in London," British Sports Minister Hugh Robertson said. "We are absolutely confident here that we can keep the event safe and secure... The best way to show solidarity with Boston is to continue and send a very clear message to those responsible."

The London Marathon, which takes in some of the city's most recognisable landmarks, draws many of the world's top marathoners, as well as tens of thousands of amateur and "fun" runners who raise money for charity.

Prince Harry, patron of the marathon's charitable trust, is scheduled to attend Sunday's race and make the presentations to the winners.

"When you have an event of any nature - a marathon, parade - it's only as safe as the city itself," race chief executive Nick Bitel said. "If it's not held in a stadium, you can't do a lockdown like you may do in a building."

Also taking place Sunday is the Bahrain Grand Prix, a Formula One race that faces its own security issues after a series of explosions, including a gas cylinder blast that set a car ablaze in the Gulf nation's financial district.

Security for the Olympics, meanwhile, has been paramount ever since the attacks by Palestinian gunmen that killed 11 Israeli athletes and coaches at the 1972 Munich Games.

The focus now falls on Sochi, a Black Sea resort that will host Russia's first Winter Olympics next February. Security was already a concern because of Sochi's proximity to an Islamic insurgency that spread across southern Russia after separatist wars in Chechnya.

"Naturally, we're beefing up security measures," Russian Sports Minister Vitaly Mutko said in remarks carried by the R-Sport news agency.