The United States has been warned by members of the terrorist Taliban army that they are out to retaliate the death of al-Qaeda leader Osama Bin Laden.

Today twin bombings near Pakistan's northwestern city of Charsadda killed 73 people, most of them police cadets, which would be considered as the largest attack since the death of Taliban leader Osama bin Laden.

The Tehreek-e-Taliban group has admitted it carried out the attacks as a first act of revenge for bin Laden's death, Pakistan's Dunya TV reported. The al-Qaeda leader was killed May 2 by U.S. Navy SEALs at a house in the Pakistani town of Abbottabad, 30 miles (50 kilometres) north of the capital, Islamabad.

"Our leader Hakimullah Mehsud has said that today's attack was reaction to Osama's martyrdom and operations by the Pakistan army in the tribal areas," Pakistan Tehreek-e-Taliban spokesman Ehsanullah Ehsan said by phoneas quoted by Bloomberg News TV from an undisclosed location. He said the attack "was the first of many bombings" that would "first target Pakistan and then the U.S."

Reports gathered said bombers targeted 15 buses carrying newly graduated members of the Frontier Constabulary, a paramilitary force, who were going home after a May 11 ceremony, said Ghufran Ali, a police official in Charsadda in Bloomberg News TV. Sixty-six of the dead are from the force, Ali said. The blasts injured at least 115 people, the Edhi rescue service said.

Pakistan's Taliban movement and allied militant groups have conducted scores of bombings and gun attacks on police, army and intelligence facilities since 2007, when the army battled armed militants in the Lal Masjid, or Red Mosque, in Islamabad.

Attacks intensified, killing thousands of Pakistani civilians and security force members, following army offensives against guerrilla strongholds from 2009.