A Pakistani doctor who helped the US track down Osama bin Laden has been convicted of high treason and sentenced to 33 years in prison, according to a government official.

Shakil Afridi was also ordered to pay a fine of about 3,500 US dollars (£2,200), said Nasir Khan. If Afridi doesn't pay, he will spend another three and half years in prison.

Mr Khan is a government official in Pakistan's Khyber tribal area, where Afridi was tried.

Afridi ran a vaccination programme for the CIA to collect DNA and verify bin Laden's presence at the compound in the town of Abbottabad, where he was killed last May by US commandos.

US secretary of state Hillary Clinton has called for Afridi to be released, saying his work served Pakistani and American interests.

Afridi's conviction comes at a sensitive time because the US is already frustrated by Pakistan's refusal to reopen Nato supply routes to Afghanistan.

The supply routes were closed six months ago in retaliation for American air strikes that killed 24 Pakistani soldiers.

Afridi was tried under the Frontier Crimes Regulations, the set of laws that govern Pakistan's semi-autonomous tribal region.

Human rights organisations have criticised the regulations for not providing suspects due process of law. There is no right to legal representation, to present material evidence or cross-examine witnesses. Verdicts are normally handed down by a Khyber government official in consultation with a council of government elders.

Afridi has the right to appeal against the verdict, said Iqbal Khan, another Khyber government official.