Questions are being asked as to how Pakistan failed to realise Osama bin Laden was hiding in a populated area near a military training academy.

Pakistan's president Asif Ali Zardari denied the country may have sheltered Osama bin Laden before he was killed by American forces, and admitted that his security forces were left out of the US operation to kill the Al-Qaeda leader.

Writing in the Washington Post, Zardari said Pakistan knew nothing about his whereabouts and insisted ten years of cooperation with the United States had led to the assisination.

U.S. President Barack Obama announced late Sunday that Osama bin Laden – the founder and head of Al-Qaida – was killed by US forces at a compound in the Pakistani town of Abbottabad, which is located close to the capital, Islamabad.

The compound is a few hundred metres from the Pakistan Military Academy, an elite military training center, which is being described as Pakistan's equivalent to the West Point academy in the US.

Irate US lawmakers wondered how it was possible for bin Laden to live in a populated area near a military training academy without anyone in authority knowing about it.

His comments in a Washington Post opinion piece Monday were Pakistan's first formal response to the suspicions by U.S. lawmakers and other critics.

"Some in the U.S. press have suggested that Pakistan lacked vitality in its pursuit of terrorism, or worse yet that we were disingenuous and actually protected the terrorists we claimed to be pursuing. Such baseless speculation may make exciting cable news, but it doesn't reflect fact," Zardari wrote.