KANDAHAR, Afghanistan - A suicide bomber blew himself up next to a police convoy in southern Afghanistan on Sunday, killing four civilians and wounding eight other people, an official said.

A U.S.-coalition member and another civilian died in a separate roadside blast, also in the south.

The suicide bomber was targeting the district police chief in Musa Qala in Helmand province, but instead killed four civilians, said provincial police Chief Mohammad Hussein Andiwal. Eight other people, including five policemen were wounded, he said.

The bomber also died. Several shops were damaged in the blast. The police chief was not harmed, Andiwal said.

The attack came a day after insurgents hit a NATO helicopter carrying the Helmand's Gov. Ghulab Mangal into the volatile town. The helicopter was damaged in the rocket-propelled grenade attack, but no one was injured.

U.S., British and Afghan troops pushed Taliban fighters out of Musa Qala late last year after the militants overran the area in early 2007 and held it for 10 months.

More than 1,200 people -- mostly militants -- have died in insurgency-related violence in Afghanistan this year, according to a tally compiled by The Associated Press.

Last year militants launched over 140 suicide missions on Afghan and foreign troops, but most victims in such attacks have been civilians.

Also Sunday, a roadside bomb hit a U.S. military vehicle in the southern Zabul province, killing one coalition service member and an Afghan civilian.

A statement from the U.S.-led coalition said another service member was seriously injured in the attack. It did not give any further details about the casualties, or say if the civilian killed was a bystander or working with the coalition.

In eastern Nangarhar province, suspected Taliban militants shot and killed two police officers Sunday in Khogyani district, said Mohammad Hashim Ghamsharik, spokesman for the provincial governor.

He said the two men had just been dispatched to Nangarhar on Saturday as reinforcements from Kabul. They walked outside their police post and were attacked by insurgents from a nearby village, Ghamsharik said.

In western Herat province, meanwhile, Afghan security forces launched a search-and-rescue operation Sunday in Adraskan district, freeing two road construction workers -- an Indian and a Nepalese -- who were kidnapped April 21, said provincial police Chief Juma Adil.

He said the chief hostage-taker was arrested.

There have been several attacks on Indian construction crews in the country.