China will further support Pakistan's efforts to combat terrorism, Foreign Ministry spokeswoman Jiang Yu said on Tuesday, after the United States confirmed it had killed Osama bin Laden in Pakistan.

Pakistan has been "at the forefront" of the international fight against terrorism, and its government has been dedicated to the cause, Jiang told a regular news briefing, adding that Islamabad's anti-terror measures have been "forceful".

"Pakistan has made an important contribution to international anti-terror efforts," she said.

Jiang said China supported Pakistan developing and implementing its strategy against terror "based on its own conditions". China is willing to enhance regional peace and stability together with South Asian countries including Pakistan, she said.

Jiang made the remarks as Pakistan faces international scrutiny since bin Laden was killed by US special forces, with questions over whether Pakistan's military and intelligence were unable to catch him or knew all along where he was hiding.

Pakistan's President Asif Ali Zardari denied suggestions his country's security forces may have sheltered bin Laden, and said their cooperation with the US helped pinpoint the world's most wanted man.

His comments in a Washington Post opinion piece on Monday were Pakistan's first formal response to suspicions raised by US lawmakers and other critics, which could further sour relations between Islamabad and Washington at a crucial point in the war in Afghanistan.

"Some in the US 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.

Ties between the two nominal allies were already strained amid US accusations that the Pakistanis are supporting militants in Afghanistan and Pakistani anger over American drone attacks and spy activity on its soil.

US Senate Armed Services Committee Chairman Carl Levin said Pakistan's intelligence and army have "got a lot of explaining to do", given that bin Laden was holed up in such a large house with surrounding buildings, the fact that its residents took the unusual step of burning their garbage and avoided any trash collection.

"It's hard to imagine that the military or police did not have any ideas what was going on inside of that," Levin said.

Zardari said Monday's raid to kill bin Laden "was not a joint operation" - the kind of which has been conducted in the past against lesser terror suspects in Pakistan - but that Pakistani cooperation, in a general sense, had helped lead them to bin Laden.

"A decade of cooperation and partnership between the US and Pakistan led up to the elimination of Osama bin Laden as a continuing threat to the civilized world," he said.

US President Barack Obama also said the country's anti-terror alliance had helped in the run-up to the operation, but did not thank Pakistan when he announced the death of bin Laden.

AP and Reuters contributed to this story.