Associated Press Honor guards carry the casket of a U.S. soldier from a C-17 Globemaster plane after its arrival from Afghanistan at Ramstein Airbase in southwestern Germany, Tuesday. The soldier was one of the four U.S. demolition specialists killed on Monday while blowing up suspected abandoned Taliban rockets near the southern Afghan city of Kandahar.

KANDAHAR, Afghanistan - A gunman opened fire yesterday on a group of U.S. troops shopping on a busy street in this former Taliban stronghold, wounding one American and an Afghan before escaping, the U.S. military and witnesses said.

Afghan officials blamed the shooting on Taliban or al-Qaida fugitives and said they feared more attacks. The shooting occurred one day before Afghanistan's former king was expected to return to the capital, Kabul, after 29 years exiled in Rome.

Mohammad Zaher Shah was to have come home last month, but his trip was postponed because of fears for his safety.

Witnesses said the Americans, who were wearing civilian clothes, were at a gun shop when the shots were fired. The Americans thought a firecracker had exploded until they noticed one of their group was bleeding, said Maj. Ralph Mills, a spokesman for U.S. Central Command in Tampa, Fla.

The wounded American, whose name was not released, walked to his vehicle unassisted, witnesses said. He was taken to the U.S. military hospital at Kandahar airport, where he was reported in stable condition.

The gun shop owner, who gave his name only as Daood, said one Afghan also was wounded. Another gunsmith, Mohammed Saleem, said the Americans left the scene quickly after the attack. He praised them for not opening fire on a street filled with children who had just left school for the day.

"If they had been Russians, maybe they would have started shooting," Saleem said. "We were surprised that the Americans were armed but didn't shoot."

Afghan troops cordoned off the area and searched for the assailant. They also warned shopkeepers to be vigilant for further attacks.

"There are still individual Taliban or al-Qaida members in the city," said Abdul Bari, a local commander. "They were probably responsible for this. We may see more such incidents in the future."

On Friday, an assailant fired a rocket at the Kandahar governor's mansion, located on a compound that includes a special forces barracks. The rocket missed the building and exploded, causing no casualties.

Special forces could be seen late yesterday on the roof of the barracks, surveying the busy streets through binoculars. Other U.S. troops, mostly from the 101st Airborne Division, are stationed at the Kandahar airport just south of the city.

Kandahar was the birthplace of the radical Taliban movement and was the last major Afghan city to fall to U.S.-backed Afghan forces last year.

During a speech yesterday at the Virginia Military Institute, President Bush warned that with the end of winter, al-Qaida forces were regrouping to stage new attacks in Afghanistan.

"As the spring thaw comes, we expect cells of trained killers to try to regroup to murder, create mayhem and try to undermine Afghanistan's efforts to build a lasting peace," Bush said.

U.S. and other international officials have warned for weeks that Westerners, especially Americans, were at risk from attack by Taliban and al-Qaida fugitives. The risk is believed greater, however, in Kabul and in provinces to the southeast where the U.S.-led coalition is hunting Taliban and al-Qaida forces.

British Royal Marines joined that operation this week, sending elite troops into the snow-covered mountains along the Pakistani border to try to cut off escape routes into Pakistan.

Yesterday, British officers said their forces had not clashed yet with al-Qaida or Taliban units. However, the Royal Marines have found thousands of rounds of ammunition, communication equipment and some documents in caves and bunkers.

Despite the ongoing tensions, the United Nations is trying to return the millions of Afghans who fled their homeland during the past two decades of armed conflict.

In Kabul, the head of the U.N. refugee agency, Rudd Lubbers, said the security situation in 80 to 90 percent of the country was safe enough for refugees to return.

However, Lubbers said efforts to bring home the remaining refugees might be slowed because his agency was running low on money.

The United Nations had predicted that 400,000 Afghans would return from Pakistan over the year. However, more than half that number came home in the past seven weeks alone, he said. The agency has budgeted $271 million for the repatriation program, only about half that amount has been received from donors, Lubbers said.