Partial results from last week's election put Afghan President Hamid Karzai ahead of main rival Abdullah Abdullah, but not by enough to avoid a second round run-off in October, figures released yesterday showed.

With 17 per cent of votes tallied, Mr Karzai held a lead of 43 per cent to 34 per cent over former foreign minister Abdullah.

The results have been trickling in over the past week, leaving the country in political limbo. To avoid a run-off, a candidate must secure more than 50 per cent of the vote.

The election is a major test for Mr Karzai after eight years in power and for US President Barack Obama, who has poured in thousands of extra troops as part of his new regional strategy to defeat the Taliban and stabilise Afghanistan.

In Kandahar, the country's second biggest city and the spiritual home of the Taliban, authorities raised the toll from a massive truck bomb late on Tuesday to 43 dead and 65 wounded, all civilians.

The bomb devastated a section of the town and was the worst in more than a year. It came the same day four American servicemen were killed, making 2009 the deadliest year for foreign forces since the overthrow of the Taliban in 2001.

Election officials have warned against drawing conclusions about the final count from the small initial samples. They have promised to provide daily updates but the complete count is not due until September 3.

The results suggest a disappointing turnout of only about 5.5 million votes in a country of some 30 million people. The total number of eligible voters is not known exactly, but election authorities put it at around 15 million.

Taliban fighters had launched attacks and threatened reprisals against voters during the election, scaring many Afghans away from the polls, especially in the violent south.