President Bush has promised Afghan President Hamid Karzai a thorough investigation of a deadly traffic accident and shooting in Kabul this week involving US troops.

Mr. Bush's chief spokesman Tony Snow told reporters the president spoke to Mr. Karzai and expressed sympathy for those killed and injured in Kabul on Monday and pledged a full investigation.

Afghan protesters throw stones at US military vehicle after traffic accident in Kabul, May 29, 2006

Afghan police say at least 20 people were killed and 160 wounded in the accident and subsequent rioting.

The U.S. military in Afghanistan has already conducted an initial probe. Spokesman Tom Collins says the probe shows that U.S. troops fired in "self-defense" on Monday after a deadly traffic accident set off rioting in central Kabul.

Collins said the mobs threw rocks and threatened U. S. forces after the accident. He also said there were shots fired from the crowd and soldiers used their weapons to defend themselves.

According to Collins, the accident took place when the brakes on a heavy U. S. military truck failed, the driver lost control and the truck plowed into several vehicles.

He said it is too early to say if the soldiers shot above the crowd or into it. Some witnesses say they saw U.S. soldiers fire on civilians.

Afghan police said political "agitators" enflamed the crowd, and "opportunists" used the riots to steal.

The Afghan parliament has passed a resolution urging the government to arrest those responsible for the accident.

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