Twin bombs kill three in Boston

Almost three-quarters of the 23,000 runners who participated in the race had already crossed the finish line when a bomb that had apparently been placed in a garbage can exploded around 2.50 pm in a haze of smoke amid a crowd of spectators on Boylston Street in the heart of the city. Thirteen seconds later,another bomb exploded several hundred feet away.

Pandemonium erupted as panicked runners and spectators scattered,and rescue workers rushed in to care for the dozens of maimed and injured,some of whom lost legs in the blast,witnesses said. The FBI took the lead role in the investigation on Monday night,and Richard DesLauriers,the special agent in charge of the bureau’s Boston office,described the inquiry at a news conference as “a criminal investigation that is a potential terrorist investigation”.

Officials in New York and Washington stepping up security at important locations. Near the White House,the Secret Service cordoned off Pennsylvania Avenue out of what one official described as “an abundance of caution”.

President Obama vowed to bring those responsible for the blasts to justice. “We will get to the bottom of this,” he said. “We will find who did this,and we will find out why they did this. Any responsible individuals,any responsible groups will feel the full weight of justice.”

He did not refer to the attacks as an act of terrorism,and cautioned people from “jumping to conclusions” based on incomplete information. But a White House official,speaking on the condition of anonymity afterward,said,“Any event with multiple explosive devices — as this appears to be — is clearly an act of terror,and will be approached as an act of terror.”

“However,” the official added,“we don’t yet know who carried out this attack,and a thorough investigation will have to determine whether it was planned and carried out by a terrorist group,foreign or domestic.”

Jarrett Sylvester,26,said that as he approached the end of the 26.2-mile race,he heard what sounded like a cannon blast. “The first one went off,I thought it was a big celebratory thing,and I just kept going,” he said. “And then the second one went off,and I saw debris fly in the air. And I realized it was a bomb… And I just took off and ran in the complete opposite direction.”

One law enforcement official said there had been four explosive devices: the two that exploded and two that were disabled by police. The official said the devices appeared to have been made with black powder and ball bearings,but that investigators were unsure how the two that exploded had been set off.

It was unclear Monday evening who might be responsible for the blast. Although investigators said that they were speaking to a Saudi citizen who was injured in the blast,several law enforcement officials stressed that no one was in custody.

The Saudi man had been seen running from the scene of the first explosion,a person briefed on preliminary developments in the investigation said on Monday afternoon. A law enforcement official later said the man,who was in the US on a student visa and came under scrutiny because of his injuries,his proximity to the blasts and his nationality,but added that his role in the attack,if any,was unclear.

Some law enforcement officials noted that the blasts came at the start of a week that has sometimes been seen as significant for radical American anti-government groups: it was the April 15 deadline for filing taxes,and Patriots’ Day in Massachusetts,the start of a week that has seen violence in the past. April 19 is the anniversary of the 1995 Oklahoma City bombing.

The bombs used in Monday’s attacks were similar in size to the device used in the 1996 Atlanta bombing but not nearly as large as the one used in Oklahoma City. In Atlanta,a pipe bomb was detonated near pedestrians,killing 2 and injuring more than 100.

The attack in Oklahoma City was far larger because the perpetrator used a truck packed with thousands of pounds of explosives. The device killed more than 150 people.

The Boston Marathon,one of running’s most storied events which typically draws half a million spectators,is held on the third Monday of April every year. The men’s race was won by Lelisa Desisa Benti of Ethiopia,who finished it in 2 hours,10 minutes and 22 seconds,but long after the world-class athletes had left,the sidewalks were thick with spectators cheering on friends and relatives as they loped,exhausted,toward the finish line.

The blast was so powerful that it blew out shop windows and damaged a window on the third floor of the Central Library in Copley Square. Dr Alasdair Conn,chief of emergency services at Massachusetts General Hospital,said several people brought in had lost their legs.

“This is like a bomb explosion we hear about in Baghdad or Israel or other tragic points in the world,” Conn said.