By Crispin Thorold
BBC correspondent in Kabul
Leaders of a south-east Afghanistan tribe have told its members they must vote for Hamid Karzai in presidential polls or their houses will be burned.
Taleban fighters have vowed to kill those intending to vote
The decision, which was made by 300 elders of the Terezay tribe, was broadcast by radio in Khost province.
Militants from the Taleban, who are active in the same area, have repeatedly threatened to kill people who do vote in next month's election.
A Karzai spokesman refused to condemn the announcement.
However, he did urge Afghans not to turn to violence during the campaign.
A tribal leader, Mubarak Shah, told the BBC that if tribal members did not vote their houses would be burned and they would not be allowed to attend local weddings and funerals.
There are widespread fears that the secret ballot, which will be held on 9 October, will be marred by violence.
Security concerns have already severely restricted campaigning.
Few of the 18 presidential candidates have held political rallies.