Foreign leaders and governments around the world are condemning the bombing at the Boston Marathon, which left at least three people dead and dozens others injured.
NATO Secretary General Anders Fogh Rasmussen expressed "deep shock" at the attack and offered condolences to those impacted. In a statement, he said his thoughts are with the people of Boston and all of the United States.
European Union President Herman Van Rompuy condemned what he called the "appalling attacks" and expressed confidence that the perpetrators will be brought to justice.
United Nations Secretary General Ban Ki-moon lamented the "senseless violence." He said the incident was even more appalling because it took place at an event known "for bringing people together from around the world in a spirit of sportsmanship and harmony."
Pakistan's Foreign Office condemned the "terrorist attacks" and said the government and people of Pakistan are "deeply shocked and saddened" by the "despicable act."
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Meanwhile, the Pakistani Taliban, which has in the past claimed responsibility for attempted attacks in the U.S., denied having any role in the Boston bombing.
Afghan President Hamid Karzai also denounced the attack "in the strongest possible terms." Offering condolences and sympathies to the families of the victims, Mr. Karzai said those in his country "feel better the pain and suffering arising from such incidents."
The Organization of Islamic Cooperation also strongly condemned what it called the "cowardly attacks." In a statement, the OIC said it has fought against terrorism in all its forms, and offered its condolences, prayers and support to the people of Boston.
In India, Prime Minister Manmohan Singh responded by expressing his "solidarity with the American people in the struggle against terrorism." In a message to President Barack Obama, Mr. Singh offered India's full support in investigating the attack.
Somali President Hassan Sheikh Mohamud spoke out against the attack on the innocent athletes and their supporters, calling the bombing "the most depraved and vicious act of cowardice."
Somali insurgent group Al-Shabab, meanwhile, mocked those injured and killed in the twin blasts. On its English-language Twitter page
, the Islamist group said the attack represents just a "tiny fraction" of the pain U.S. soldiers inflict on innocent Muslims around the world.
No one has yet claimed responsibility for the bombing.
In this image from video provided by WBZ-TV, spectators and runners run from what was described as twin explosions that shook the finish line of the Boston Marathon, April 15, 2013.
An emergency responder and volunteers, including Carlos Arredondo in the cowboy hat, push Jeff Bauman in a wheel chair after he was injured in an explosion near the finish line of the Boston Marathon April 15, 2013.
Medical workers transport the injured across the finish line during the 2013 Boston Marathon following an explosion, April 15, 2013.
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion, April 15, 2013.
One of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon is investigated by two people in protective suits in the wake of two blasts in Boston April 15, 2013.
Runner John Ounao cries when he finds friends after several explosions rocked the finish of the Boston Marathon, April 15, 2013.
A police officer clears Boylston Street following an explosion at the finish line of the 2013 Boston Marathon, April 15, 2013.
Medical workers aid a wounded woman at the finish line of the 2013 Boston Marathon following two explosions there, April 15, 2013.
Medical workers aid injured people at the finish line of the 2013 Boston Marathon following an explosion in Boston, April 15, 2013.
A woman is comforted by a man near a triage tent set up after explosions went off at the 117th Boston Marathon, April 15, 2013.
A Massachusetts state police officer guards the area containing the medical tent, rear, following an explosion at the 2013 Boston Marathon, April 15, 2013.
An unidentified Boston Marathon runner leaves the course crying near Copley Square following an explosion, April 15, 2013.
A Boston police officer wheels in injured boy down Boylston Street as medical workers carry an injured runner following an explosion during the 2013 Boston Marathon, April 15, 2013.
Justine Franco of Montpelier, Vermont, holds up a sign near Copley Square looking for her missing friend, April, who was running in her first Boston Marathon, April 15, 2013.
President Barack Obama leaves the podium after speaking in the press briefing room at the White House, April 15, 2013, following the explosions at the Boston Marathon.