The Pakistani Taliban, which claimed the 2010 Times Square bomb plot, on Tuesday denied anything to do with explosions that killed three people and wounded more than 100 in Boston.
"We believe in attacking US and its allies but we are not involved in this attack," Tehreek-e-Taliban Pakistan (TTP) spokesman Ehsanullah Ehsan told AFP.
"We have no connection to this bombing but we will continue to target them wherever possible," Ehsan added.
Monday's explosions at the Boston Marathon, one of America's top sporting events, forced cities from New York to Los Angeles to go on high alert and conjured up memories of the September 11, 2001 attacks.
An Internet video purportedly from the TTP claimed responsibility for a car bomb attempt in New York's Times Square on May 1, 2010, for which Pakistani-American Faisal Shahzad was jailed for life.
A TTP spokesman later denied that the faction had trained or recruited Shahzad.
Shahzad said during his trial that he received bomb-making training during a 40-day stay with the Pakistani Taliban, but that on his return to the United States he planned the bombing and acted alone.
He was also shown in a video embracing Hakimullah Mehsud, commander of the TTP, who has vowed to attack major US cities.
The TTP is based in Pakistan's northwestern tribal belt on the Afghan border and has been blamed for some of the deadliest suicide attacks in Pakistan.
US President Barack Obama says it is not yet clear who was behind the blasts. He said the perpetrators would pay. He did not utter the word "terror".