Pakistani authorities were searching tonight for their country's Ambassador to Afghanistan and two nuclear officials who appear to have been kidnapped separately in the tribal areas of northwestern Pakistan.

Police were also interrogating Mullah Mansour Dadullah, a top Taleban commander who was captured in the northwest yesterday, amid reports that Islamist militants had offered to swap him for the Ambassador.

The envoy is one of the most senior government officials to have been kidnapped in Pakistan's tribal areas.

The apparent abductions highlight the security risks in nuclear-armed Pakistan as it prepares for parliamentary elections on Monday that are being seen as a test of President Pervez Musharraf's popularity and commitment to democracy.

Pakistan's Army is locked in a conflict with Taleban and al-Qaeda militants based in northwestern Pakistan whom President Musharraf blames for the assassination of Benazir Bhutto in December.

Tariq Azizuddin, the Pakistani Ambassador to Kabul, was driving there with his driver and a bodyguard yesterday when they disappeared in Pakistan's lawless Khyber tribal district, local officials said.

Pakistan's Embassy in Kabul said that it last had contact with Mr Azizuddin yesterday morning as he was travelling into Khyber district - long a hotbed of bandits and smugglers - from the northwestern city of Peshawar.

“Our law enforcement and other agencies in Khyber are carrying out a search operation,” said Javed Iqbal Cheema, the Interior Ministry spokesman.

“We hope we should be able to trace and recover him soon.”

Police also confirmed that two technicians from the Pakistan Atomic Energy Commission had been abducted at about the same time by masked men near the northwestern town of Dera Ismail Khan in North West Frontier Province.

The technicians were on their way to do a routine geological survey in the area when they were kidnapped along with their driver and five local people, who have now been released, local police said.

Pakistani officials declined to say if Mr Azizuddin had been kidnapped, but Afghanistan's President, Hamid Karzai, said that he was sure that the envoy had been abducted.

“May God make it happen that our brother and neighbouring country, Pakistan, is able to rescue him from the abductors, the terrorists,” Mr Karzai said during a conference on education in Kabul.

“I hope he is safe and I hope he will be released soon.”

It was not immediately clear, however, whether the alleged abductors were Islamist militants or members of a criminal gang simply out to make money.

Khyber is notoriously lawless, and scores of people were killed there late last year in fighting between tribal militants loyal to two rival clerics.

But the region has been relatively free of the sort of militant activity that has engulfed neighbouring areas such as North and South Waziristan, and the Swat Valley.

Four Pakistani employees of the International Committee of the Red Cross went missing in the same region this month and have still not been found.

Tens of thousands of troops began fanning out across Pakistan today to improve security before next week's vote.

But fears of election violence mounted after a bomb exploded near the office of a candidate in the southwestern province of Baluchistan, injuring at least nine people.

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