The Pakistan Taliban, which claimed responsibility for a 2010 bomb plot in New York, has denied involvement in the Boston marathon attack.
A spokesman for the militant outfit said that while it supported attacks on the US and other nations, it was not behind Monday's assault that killed three people and left more than 140 injured.
"We believe in attacking US and its allies but we are not involved in this attack," a spokesman for the Tehrik-i-Taliban Pakistan (TTP), Ehsanullah Ehsan, told the AFP.
Speaking from an undisclosed location, he added: "We have no connection to this bombing but we will continue to target them wherever possible."
In the spring of 2010, an online video apparently produced by the Taliban claimed responsibility for a failed plot to attack Times Square, though a spokesman subsequently denied it. Pakistani-American Faisal Shahzad was later jailed for life for plotting the attack.
During his trial, Mr Shahzad said he had had received bomb-making training during a 40-day stay with the Pakistani Taliban. He was also shown in a video embracing Hakimullah Mehsud, commander of the TTP, who has on several occasions announced plans to attack major US cities
Mr Shahzad said that upon his return to the US from Pakistan's tribal areas he planned the bombing and acted alone. He had left a vehicle packed with explosives in Times Square. Street vendors spotted smoke coming from the vehicle and contacted police.
"It's a war. I am part of the answer to the US terrorising the Muslim nations and the Muslim people," Shahzad later told a judge.
While reports suggest investigators in Boston are following various leads, no individual or group has claimed responsibility for the double blast.
White House officials told reporters the attack was being treated as an act of "terrorism" though President Obama was careful not to use the word or to speculate about who may have been responsible when he spoke.
"We will find out who did this. We'll find out why they did this," he said. "Any responsible individuals, any responsible groups, will feel the full weight of justice."
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