Tens of thousands of Pakistanis inched towards Islamabad Monday, in a protest march led by an influential cleric calling for revolution but accused by the government of trying to sow political chaos ahead of elections.

Tahir-ul Qadri, a Pakistani-Canadian who returned to his homeland last month after years in Toronto, accuses the government of being corrupt and incompetent, and says polls cannot be held until reforms are enacted.

U.S. drone strikes targeting a militant compound in Pakistan's northwestern tribal area killed at least five insurgents Sunday, security officials said, the second attack in 24 hours.

Two U.S. drones fired four missiles at a house belonging to a militant commander in Wacha Dana town, 10 kilometers (six miles) west of Wana, the main town in the South Waziristan tribal district near the Afghan border, Pakistani security officials said.

Talks between NATO chief Anders Fogh Rasmussen and Pakistani President Asif Ali Zardari were canceled Saturday as Islamabad appeared headed for a clash with the U.S. over reopening Afghan supply routes.

Both NATO and Pakistani officials insisted to AFP that the last-minute delay in the planned meeting in Chicago was due to the late arrival of Zardari's flight from London.

High-level talks on ending a diplomatic deadlock between the United States and Pakistan have ended in failure over Pakistani demands for an apology from the United States, The New York Times reported Saturday.

The newspaper said U.S. special envoy to Afghanistan and Pakistan Marc Grossman left the Pakistani capital Friday night with no agreement.

Pakistan's intelligence service believes it deserves credit for helping U.S. spy agencies locate the hideout of Osama bin Laden, who was killed by U.S. commandos nearly a year ago, The Washington Post reported.

"The lead and the information actually came from us," an unnamed senior official with Pakistan's Inter-Services Intelligence Directorate (ISI) told The Post.

President Asif Ali Zardari became the first Pakistani head of state since 2005 to visit India on Sunday for a one-day trip he described as "very fruitful" in improving ties between the rivals.

During a visit billed as private but of great diplomatic significance, Zardari lunched with Indian Prime Minister Manmohan Singh and invited him to visit Pakistan.

A Pakistani court on Monday sentenced Osama bin Laden's three widows and two of his daughters to 45 days detention for illegal residency and ordered their deportation as soon as possible.

Their lawyer Mohammed Aamir said the period of detention began on March 3, when they were formally arrested on charges of illegal entry and residency in Pakistan and that they would continue to be held at their villa in Islamabad.

Several thousand Pakistanis poured onto the streets of Islamabad Monday, chanting "death to America" and demanding holy war at a rally whipped up by right-wing, religious and banned organizations.

It was the latest show of support for Defense of Pakistan, a coalition of around 40 parties chaired by a cleric dubbed the father of the Taliban that include organizations blacklisted at home and abroad as terror groups.

Republican presidential hopeful Newt Gingrich said Wednesday that Pakistan's nuclear arsenal was at risk of being seized by "extremists" who had probably infiltrated Islamabad's military.

"My guess is that they have well over 100 nuclear weapons and that the Pakistani military is so penetrated by extremist elements you have no idea if one morning, they are going to lose three or four of them. I mean just have them stolen," Gingrich told CNN's Situation Room program.

A former town mayor, his son and bodyguard were killed and eight other people wounded on Monday when a suicide bomber blew himself up in Pakistan's northwest, police said.

The bomber targeted Hanif Khan Jadoon in Swabi, 90 kilometers east of Peshawar, as he was sitting in his car after offering his Eid prayer.