Pakistan is sending a delegation to Afghanistan on Monday to try to persuade the ruling Taleban to surrender Osama Bin Laden, the man identified by the United States as the chief suspect for Tuesday's suicide attacks.

The envoys are flying with special UN permission to Kandahar, the base of the Taleban's reclusive leader Mullah Mohammad Omar, to warn that Mr Bin Laden must be handed over if US military strikes are to be averted.

The Taleban has both now and in the past refused to surrender Mr Bin Laden, saying that the US has no proof of his involvement in the plane suicide mission, or other attacks.

Pakistan has attempted before to persuade the Taleban to change their minds, but the BBC Islamabad correspondent says this time the stakes are much higher and the country will be under heavy pressure from Washington to succeed.

Pakistan radio now says its border has been sealed to prevent more refugees crossing in from Afghanistan. Iran has taken similar action.

And in further signs of unease, Pakistan's stock markets are closing for three days to avert a feared major slide in its currency.

Pakistan's decision to support Washington has prompted protests from hardline Islamic groups.

Several hundred demonstrators near the Afghan border burned US flags and shouted their support for Mr Bin Laden.

The leader of one party threatened to organise suicide attacks against US interests if American troops used Pakistani soil for a military operation.