KANDAHAR, Afghanistan - An explosion near a U.S. military vehicle in southern Afghanistan today wounded four American troops, a U.S. military spokesman said, the latest in a series of bloody assaults on coalition forces.

The vehicle was hit on a highway near the main southern city of Kandahar. A local Afghan police chief said the blast was a suicide attack. The U.S. military confirmed it was a bombing, but gave no further details.

Spokesman Col. James Yonts told reporters in Kabul that the four wounded, one in serious condition, were flown to a U.S. base in Kandahar for medical treatment.

Gen. Salim Khan, the deputy police chief for Kandahar city, said a suicide bomber had rammed a car full of explosives into the U.S. vehicle. The head of the attacker was found near the site of the blast and it appeared to be that of an Arab, he said.

Three other bombs were found hidden on roadsides around Kandahar this morning, a government official in the city said. All were defused, he said.

A bomb attack Sunday on an Afghan family's pickup truck just north of Kandahar killed a woman and wounded four others, including two children, said Khan, the deputy police chief. He said the attackers may have thought the four-wheel-drive vehicle belonged to the Afghan army.

A purported Taliban spokesman, Mullah Latif Hakimi, said in a telephone call to AP that the group was responsible for today's bombing and that the suicide attacker was an Afghan.

Hakimi often calls news organizations to claim responsibility for attacks on behalf of the Taliban. His information has sometimes proven untrue or exaggerated, and his exact tie to the group is unclear.

Taliban-led rebels have stepped up attacks in an apparent effort to sabotage legislative elections due in September. Five American troops have died in attacks this month.

On June 1, a suspected al-Qaida suicide bomber killed 20 people at the funeral of an anti-Taliban cleric in Kandahar, one of the worst terror attacks here since the Taliban was ousted in 2001.