Afghan officials say Taleban guerrillas have ambushed a police convoy in southern Afghanistan, killing three officers.

Officials say at least 11 Taleban insurgents were also killed during the ambush and subsequent fighting in Helmand province.

In Kabul, a roadside bomb killed four healthcare workers employed by the Afghan Health Development Service. Police and aid officials say a doctor, a male and a female nurse and their driver were killed Monday as they were traveling in Wardak province, about 50 kilometers west of the capital.

Insurgents linked to the ousted Taleban regime have been blamed for a series of attacks on schools as well as health and development workers.

Taleban insurgents intensified their attacks this past week and so did U.S.-led coalition forces who are trying to destroy Taleban hideouts. More than 250 militants, Afghan forces, coalition soldiers and civilians were killed as a result.

Afghan officials say some 16 civilians were killed in coalition air raids Monday on a Taleban stronghold in Kandahar province. President Hamid Karzai's office says he plans to summon the commander of U.S. forces in Afghanistan to complain about the civilian casualties. Mr. Karzai, who is visiting the United Arab Emirates, has also ordered Afghan authorities to investigate the circumstances of the civilian deaths.

Some information for this report was provided by AP and Reuters.