KABUL (Reuters) - Afghans have braved threats of Taliban attacks to begin voting in a historic presidential election that they hope will mark the beginning of the end to a quarter century of conflict.

Heavily guarded polling stations in Afghanistan opened at 7:00 a.m. (3:30 a.m. British time) and will close at 4:00 p.m. on Saturday, although Afghan refugees in neighbouring Pakistan started voting half an hour earlier.

Hamid Karzai, the U.S.-backed leader of the interim government formed after the Taliban was driven from power in late 2001, is widely expected to retain the presidency. But whether he will get the 51 percent needed to avoid a November runoff is unlikely to be known until late-October.