Pakistan's main opposition party is stepping up calls for the prime minister and president to resign over the breach of sovereignty by U.S. forces who slipped in from Afghanistan to storm the compound where bin Laden was holed up, as the prime minister prepared to "take the nation into confidence" on the crisis in a parliament address.

"We want resignations, not half-baked explanations," an official of former prime minister Nawaz Sharif's Pakistan Muslim League told the News daily.

Pakistan welcomed the death of bin Laden, who plotted the Sept. 11, 2001, airliner attacks on the United States, as a step in the fight against militancy but also said the U.S. raid to kill him was a violation of its sovereignty.

Pakistan has also been embarrassed by the killing of bin Laden by U.S. special forces who found him hiding in a high-walled compound in Abbottabad town, 50 km (30 miles) north of the capital.

Former cricket star Imran Khan, who leads a small but strident nationalist party, weighed in on President Asif Ali Zardari and the unpopular government of Prime Minister Yusuf Raza Gilani for "policies based on lies and propaganda".

Khan said in a commentary that Western allies were "pointing accusatory fingers at us as harbourer of terrorists", though the United States has stopped short of accusing Pakistan of providing shelter to the world's most-wanted man.

U.S. President Barack Obama said on Sunday that bin Laden likely had "some sort" of a support network inside Pakistan, but added it would take investigations by Pakistan and the United States to find out just what the nature of that support was.

The discovery of the world's most wanted man living a short distance form Pakistan's main military academy has led to accusations of either incompetence on the part of its intelligence service, or complicity in sheltering him.

"We think that there had to be some sort of support network for bin Laden inside of Pakistan. But we don't know who or what that support network was," Obama said.