U.S. soldiers guarding the American Embassy in Kabul shot and killed at least three Afghan soldiers Wednesday as they unloaded weapons destined for a nearby intelligence depot, apparently mistaking the men for assailants, Afghan officials said. The shootout erupted as the Afghan forces were taking the weapons off a truck, said Kabul Police Chief Basir Salangi. "It was a misunderstanding between the American guards at the U.S. Embassy and our soldiers who were unloading weapons," Salangi told The Associated Press. Salangi said three Afghan soldiers were killed and two wounded. Gen. Abdul Raouf Taj, chief commander for the Kabul district where the embassy is located, said four Afghan soldiers had been killed and four wounded. Salangi said there were no apparent U.S. casualties. Tension has been high in the Afghan capital in recent months. There was an explosion not far from the U.S. Embassy in April, and a rocket slammed into the nearby headquarters of international peacekeepers on March 30. Neither attack caused any casualties. U.S. Embassies around the world are on heightened alert following a decision by Washington to raise the terrorism alert to orange, signifying a "high" risk of attacks. Also Wednesday, President Bush's special envoy to Afghanistan, Zalmay Khalilzad, was due to visit Afghanistan. It was not clear if he was in the capital at the time of the shooting. U.S. and Afghan forces sealed off the area around the embassy following the shooting, with Afghan military vehicles blocking streets leading to the U.S. compound. Salangi said the soldiers were delivering the weapons to an intelligence agency barracks across from the embassy. "They wanted to unload the weapons to store them inside the brigade, which belongs to the intelligence service," he said. U.S. embassy and Afghan government officials had no immediate comment. Maj. Sarah Wood, a British spokeswoman for the international peacekeepers that patrol the capital, said the shooting was being investigated. **PHOTO CAPTION*** An Afghan soldier yawns as an American soldier watches a military parade at a military base in Kabul, Afghanistan, on Thursday, May 15, 2003. (AP Photo/Silvia Izquierdo)