SHIGAL, Afghanistan  - Eleven children and a woman were killed by an air strike during a Nato operation targeting Taliban commanders in eastern Afghanistan, officials in the region said Sunday.

Civilian deaths have been a long-running source of friction between Afghan President Hamid Karzai and his international backers. Karzai has forbidden Afghan troops from calling for air strikes and Nato advise crews not to fire at or bomb in populated areas.

Six insurgents - two of them senior Taliban leaders - were killed during the operation in a village in Shigal district in Kunar province, which is on the Pakistani border, on Saturday, the Interior Ministry said in a statement.

The Interior Ministry did not mention any civilian casualties but Wasefullah Wasefi, a spokesman for the provincial governor, said civilian homes had been hit during an air attack. “Eleven children and a woman were killed when an air strike hit their houses,” Wasefi said.

The deaths came on the same day that a car bomb killed five Americans, including three US soldiers, a young diplomat and a US Defence Department contractor, in the southern province of Zabul. Mohammad Zahir Safai, the Shigal district chief, said the woman and the children were killed when the houses collapsed on them.

A spokesman for the Nato-led International Security Assistance Force (ISAF), Captain Luca Carniel, said they were aware of reports of civilian casualties and was assessing the incident. Carniel said ISAF had provided “air support” during the operation but he said there had been no ISAF troops on the ground. The air strike had been requested by coalition forces, not their Afghan allies, he said.

A Reuters journalist saw bodies of 11 children when they were taken to Safai’s office in protest by their families and other villagers on Sunday. The journalist did not see the body of a women and Safai said residents told him of the death. Women’s bodies are not displayed, according to custom.

Wasefi also said an American civilian adviser to the Afghan intelligence agency, the National Directorate of Security, had also been killed in the operation. He said it had lasted several hours.

The Ministry of Interior said the two dead Taliban commanders, Ali Khan and Gul Raouf, planned and organised attacks in Kunar.

The latest strike came a day after at least five Americans, including a young female diplomat, were killed in two Taliban attacks in the country’s east and south.

A suicide car bomber struck a Nato convoy in the southern province of Zabul Saturday, killing three US soldiers and two civilians, one of whom was a female US diplomat. They were travelling with Afghan officials to distribute books to students. The nationality of the second civilian was unclear.

Another US civilian was killed in an attack in the east, making it the deadliest day for the coalition since July 8 last year.

Though the Taliban have not yet announced their “spring offensive”, which started last year with a barrage of bloody attacks in early May, the traditional Afghan fighting season is beginning as the cold winter recedes.

US-led coalition forces are winding down their operations before a scheduled withdrawal of the bulk of their 100,000 troops by the end of 2014, and racing to prepare Afghan forces to take over responsibility for security.

But a brazen attack last Wednesday - when Taliban gunmen killed 46 people at a court in the western city of Farah to try to free insurgents standing trial - raised further questions about the Afghans’ ability to secure the country.