Afghan officials say a NATO air strike in northern Afghanistan has killed at least nine civilians.  It is the second time in as many days that NATO or U.S. forces may have accidentally killed civilians.  Correspondent Benjamin Sand has more from VOA's South Asia bureau in Islamabad.

Afghan authorities say suspected Taleban insurgents targeted a NATO base late Sunday in Kapisa province, just north of Kabul.  When the western forces returned fire local officials say they apparently hit a civilian house killing at least five women and several young children.

A NATO spokeswoman refused to confirm the incident, but said the matter is under investigation.

Afghan men shout anti-American slogans after car bomber attacked American convoy in Barikaw in Nangarhar province, eastern Afghanistan, 4 Mar 2007

The case comes a day after U.S. Marines reportedly killed at least nine other civilians during a violent struggle near the eastern city of Jalalabad.  The Marines say they opened fire after an explosive-packed vehicle rammed their convoy and militants attacked with machine guns.

Spokesman Major Chris Belcher says civilians were killed in the exchange.

"There are reports of death and injuries to Afghan nationals confirmed by Afghan and coalition authorities," Belcher says.

Witnesses say American soldiers fired indiscriminately into groups of Afghan cars and pedestrians as they tried to escape the area.

Protests erupted almost immediately after the attack.  Hundreds of demonstrators reportedly blocked off key roads as they chanted anti-American and anti-western slogans.

Afghan President Hamid Karzai Monday promised a thorough and independent investigation.

The United Nation's Assistance Mission in Afghanistan, known as UNAMA, also said it would be issuing its own report on the incident.  U.N. spokesman, Adrian Edwards, urged restraint until all the facts are known.

"UNAMA is deeply saddened at the woundings and the loss of life and we would like to appeal to everyone for calm so the events can be properly looked into and understood," Edwards says.

The two cases have sparked widespread concerns of a possible bloody backlash in the days ahead.

President Karzai has repeatedly denounced U.S. and coalition military action that harms civilians.

U.S. and NATO troops are in Afghanistan to provide security and fight a militant insurgency by the Taleban, which was ousted from power in 2001.