Boston, April 16 (IANS): The international community condemned the bombings at the Boston Marathon Monday, which killed three people and injured more than 100 and forced many US cities to step up security.

UN Secretary-General Ban Ki-moon Monday said the bombing "is all the more appalling for taking place at an event renowned for bringing people together from around the world in a spirit of sportsmanship and harmony".

Speaking at a ceremony at UN headquarters commemorating the 19th anniversary of the Rwanda genocide, Ban called the Boston Marathon explosions "senseless violence", reported Xinhua.

"For now I just wanted to say that my thoughts are with everyone in Boston," Ban said, expressing his deepest condolences to the families of the victims and wishing those wounded a speedy recovery.

Canadian Prime Minister Stephen Harper said he was shocked to learn of the explosions.

"It is truly a sad day when an event as inspiring as the Boston Marathon is clouded by such senseless violence," Harper said.

"Our thoughts and prayers are with those injured or affected by this horrible incident. We stand with our American neighbours in this difficult time," he said.

Australian Prime Minister Julia Gillard said Tuesday that they have been shocked by the tragic scenes in the US.

Speaking at a press conference in Canberra, she condemned this "brutal and senseless attack".

"Australia unreservedly condemns the brutal and senseless attack on what is a great event known around the world, and one people participate in to have fun as their families and friends watch on," Gillard said.

President Barack Obama said his government has not yet got "all answers" about the Boston explosions, but vowed to hold all those behind them accountable.

He also said the government has taken steps to beef up security across the country following the two blasts that happened at around 3 p.m. and went off within seconds of each other near the Boston Marathon finish line.