More than a dozen people have been killed and many more wounded when a man on a motorcycle blew himself up in a market in Helmand province, Afghan and international officials said.

Thirteen Afghans, including three police officers, were killed and at least 23 others wounded, Daud Ahmadi, a spokesperson for the province, said on Wednesday.

US General John Allen condemned the attack in Kajaki district and said it was evidence that the fighters had "declared outright war" on the Afghan people, and that it signalled the Taliban's leader had "lost all control" of his footsoldiers.

"With today's horrendous attack at the Kajaki Sofla Bazaar, insurgents have once again destroyed the lives of dozens of innocent Afghan civilians," he said in a statement.

"[Taliban leader Mohammad] Mullah Omar has lost all control over Taliban insurgents, otherwise he would immediately denounce these attacks and order his forces to stop attacking innocent Afghan civilians," Allen said.

Seperate attacks

Farther south in Helmand province, an Afghan intelligence official in Nad Ali district and two of this bodyguards were killed in an explosion, Ahmadi said.

A remote-controlled bomb was detonated as the intelligence official, Wali Mohammad Khan, walked out of his house.

He was the third local government official to be assassinated this week in southern Afghanistan, the birthplace of the Taliban insurgency.

On Tuesday in neighboring Kandahar province, a member of the Dand district council was assassinated while praying in a mosque in Kandahar city, and a member of the district council in Panjwayi was killed by gunmen on a motorbike.

Separately, NATO is investigating reports that five civilians, including one woman and two children, were accidentally killed during a night raid earlier this week in northeastern Afghanistan.

Sayed Fazelullah Wahidi, governor of Kunar province, said coalition helicopters fired into a compound on Monday night in Chawkay district, killing two fighters and the five civilians.

Karzai has repeatedly demanded an end to night raids, saying that Afghan citizens cannot feel secure if they think armed soldiers might burst into their houses in the middle of the night.

Meanwhile, Afghan security forces said they had killed nine fighters and captured 23 suspects in a series of raids in the past 24 hours.

An interior ministry statement said the operations in eight different provinces also uncovered caches of weapons, ammunition and explosives.