KABUL: Two bomb blasts have killed up to 14 Afghan civilians, including 11 members of one family, authorities said Thursday, as extremist attacks increased ahead of elections next week.

The blasts occurred Wednesday in the southern provinces of Helmand and Kandahar -- Taliban strongholds where thousands of Western troops have been battling to subdue multiple areas ahead of the polls on August 20.

In the deadliest blast, a roadside bomb struck a minivan in Helmand, said provincial government spokesman Daud Ahmadi.

"As a result, 11 civilians on board -- all members of one family -- were killed. Only one little girl around six years old survived," he told AFP.

"At this stage we do not have exact breakdown of how many women, children and men were killed but all we know is that all 11 were members of a family and were related."

The interior ministry confirmed the blast but put the death toll at nine.

Another roadside bomb killed three children as they were playing in Kandahar on Wednesday, police said.

"All the three children are boys between six and 11 years of age," said provincial police chief Mohammad Shah Khan.

Civilians bear the brunt of Afghanistan's Taliban-led insurgency, which has reached record proportions in the eight years since the 2001 US-led invasion overthrew their regime and installed a Western-backed administration.

The United Nations has said more than 1,000 civilians were killed during the conflict in the first six months of 2009, up almost a quarter over the same period last year.

Nearly 60 percent of civilian deaths were caused by insurgent attacks, most often bombings, and 30 percent by pro-government military forces, the UN said.

Afghanistan's second presidential poll and concurrent provincial council elections are being held on August 20.

Thousands of troops are operating in several districts in a bid to make it safe for people to vote, but authorities are worried that Afghans will nonetheless not dare to go to polls, undermining the credibility of the ballot.