Former prime minister Nawaz Sharif and cricket star Imran Khan made final impassioned appeals for votes before thousands of supporters Thursday as campaigning wrapped up for Pakistan's landmark elections.

Their back-to-back emotional speeches capped a frenetic campaign overshadowed by Taliban threats against polls marking the first democratic transition after a civilian government completes a full term in office.

The final day of the campaign took another dramatic turn Thursday when gunmen kidnapped a son of a former prime minister Yousuf Raza Gilani, killing his secretary and one of his bodyguards, and wounding four other people.

Frontrunner Sharif, head of the centre-right Pakistan Muslim League-N (PML-N) told crowds in the city of Lahore that he would change the country's destiny if elected, promising loans and vowing to reverse economic stagnation.

Addressing a hometown crowd estimated at 6,000-8,000 by police, Sharif's voice cracked with emotion as he said: "On May 11, God willing, the Muslim League will form a government. It is not long now."

"If you give us five years, you will see that we can change the fate of this country," he said, bellowing into a microphone between snatches of music.

Khan, who addressed supporters in the capital Islamabad by videolink from a hospital bed, drew a crowd of almost 30,000 as he delivered a deeply personal speech to cap an electric campaign as he seeks a political breakthrough.

"God will not take me from this world until a new Pakistan is built," he said, having been ordered to remain immobile by doctors with fractured vertebrae after falling at a rally on Tuesday.

Khan managed to silence the crowd as he spoke about personal sacrifices, the break-up of his marriage and his vision of a reformed, corruption-free Pakistan.

Waqas Jalil Bhatti, 26, a student of business administration, said: "It was very inspiring. I hope people will follow him. It is a chance for a new Pakistan and we should not let it go."

Sharif, bidding for an historic third term as prime minister, is considered most likely to win Saturday's polls.

Some believe the main outgoing Pakistan People's Party (PPP) can still emerge as the second largest party thanks to a rural vote bank, despite a lacklustre and rudderless campaign with a leader -- Bilawal Bhutto Zardari -- too young to stand.

The vote will be a democratic milestone in a country ruled for half its history by the military. But the campaign has been marred by Taliban threats and attacks which have killed more than 100 people since mid-April.

Despite his electrifying campaign, a question mark hangs over how well Khan will do, considering he won only one seat in 2002. He boycotted 2008 polls.

The speeches came at the end of a dramatic day which saw Ali Haider Gilani, a 27-year-old son of the ex-prime minister, kidnapped in the central city of Multan.

"People came on a motorbike. They also had a car with them and they opened fire and abducted Yousuf Raza Gilani's son Ali Haider in a black Honda," police officer Khurram Shakur told reporters.

The ex-premier's family is one of the most powerful in Multan and a key clan in the PPP. The party's campaign for re-election has been dramatically curtailed by threats from the Pakistani Taliban.

The insurgents, who have dismissed the elections as unIslamic, say they have sent suicide bombers to mount attacks on polling day.

There was no claim of responsibility for the abduction of Haider, a provincial assembly candidate for the secular PPP. Two of his brothers are standing for the national assembly.

Gilani senior was disqualified after being sacked and indicted by the Supreme Court last year for refusing to reopen corruption cases against the president.

Police told AFP the abduction was under investigation "from different angles, including the possibility of election rivalry".

Isolated attacks on Thursday killed six other people, including two attacks which targeted a PML-N candidate and the right-wing Jamiat Ulema-e-Islam party, officials said.

There was no claim of responsibility, but Taliban leader Hakimullah Mehsud has personally ordered suicide bombings on polling day, one of his commanders told AFP.

AFP saw a copy of a letter apparently sent from Mehsud to Taliban spokesman Ehsanullah Ehsan, mapping out the nationwide plan for bombings.