KANDAHAR: Roadside bombs and insurgent attacks killed 16 Afghan civilians, five policemen and two members of the U.S.-led coalition in southern Afghanistan where militants are trying to reclaim territory, Afghan and NATO authorities said Sunday.

The civilians, including women and children, were killed in Arghistan district, along Afghanistan's border with Pakistan, Kandahar province spokesman Ahmad Jawed Faisal said.

One bomb exploded when a minivan ran over it on Sunday morning, he said. A second went off when other civilians, who were riding on a tractor, arrived to help the dead and wounded.

Authorities were trying to determine how many people died in each blast. At least three other civilians were injured in the explosions.

According to the United Nations, last year was the deadliest on record for civilians in the Afghan war, with 3,021 killed.

The number of Afghan civilians killed dropped 36 percent in the first four months of this year compared with last year, but the U.N. says that too many are still being caught up in violence.

The policemen were killed while responding to a gun battle being waged against insurgents early Sunday at a checkpoint in Musa Qala district of Helmand province.

Daoud Ahmadi, the spokesman in Helmand, said a group of Taliban fighters attacked the police checkpoint at about 3 am.

Afghan police called for reinforcements, but on the way, one of the police vehicles hit a roadside bomb, killing the five policemen.

Ahmadi says three other policemen were wounded in the four-hour gun battle against the insurgents. He says the bodies of 20 insurgents were recovered from the battlefield.

Separately, a Nato service member was killed in another roadside bomb explosion Saturday in southern Afghanistan.

Nato did not disclose where the blast occurred, or provide the nationality of the soldier killed.    So far this year, 224 Nato service members have been killed in Afghanistan.