Kabul: A roadside bomb killed four civilians in southern Afghanistan on Saturday during a day of violence which also saw the deaths of two ISAF service members and an attempted suicide bombing.

"Four male civilians were killed and one injured when their vehicle hit a Taliban-planted mine in Trinkot city this morning," said Gulab Khan, a police chief from the Uruzgan province.

There was no immediate claim of responsibility for the attack, but roadside bombs are frequently planted by Taliban-led insurgents fighting a decade-long war against NATO-led foreign troops and Afghan government forces.

"Those responsible for this shameful attack must be held to account for their actions against the people of Afghanistan," said ISAF commander General John Allen.

In a separate incident in the same city police shot dead a man wearing a suicide vest.

"A suicide bomber and his accomplice were on a motorbike and wanted to target a local police commander," Khan said.

"They were identified by police who opened fire and killed them. Nobody else was hurt."

Meanwhile the International Security Assistance Force announced the deaths of two service members in separate IED (improvised explosive device) attacks, both also in the volatile south of the country. The nationalities were not released in line with policy.

The deaths bring the toll for foreign troops in 2011 to 565.

The attacks followed another roadside bomb attack on Thursday which killed a local police commander in the southern province of Kandahar. The Taliban claimed responsibility.

"Last night a police vehicle hit a roadside mine in Spin Boldak district. As a result a border police commander was killed and two of his bodyguards were injured," said provincial police Chief General Abdul Razeq.

There are around 130,000 international troops, mainly from the United States, in Afghanistan helping government forces combat the insurgency.

The United Nations said the number of civilians killed in violence in Afghanistan rose by 15 per cent in the first six months of this year to 1,462, with insurgents blamed for 80 percent of the killings.