KANDAHAR, Afghanistan (Reuters) - At least 13 civilians were killed in a roadside bomb in southern Afghanistan on Monday two days after a presidential election, a local official said.

"A roadside bomb exploded underneath a civilian van, killing all 13 on board," said Mr Dawa Khan Minapal, a spokesman for the Kandahar governor.

He said foreign troops had blocked the main road after a separate car bomb explosion earlier, prompting the van to use a dirt road where the home-made bomb was planted.