MASERU, Lesotho (AP) _ Invited in by the beleaguered government of this nation, South African forces encountered unexpected resistance Tuesday from rebellious Lesotho troops in their first military incursion since apartheid.

At least 10 soldiers and five civilians died in heavy fighting.

Furious gunfire and artillery rounds forced 20 armored South African vehicles equipped with cannons to retreat and scuttle an attempt to reinforce troops at a barracks near the capital's airport, where a day-long firefight raged.

The anti-government forces also used antiaircraft and small-arms fire against South African helicopters carrying troops to battles at military bases, Maj. Ben van Zyl said.

About 600 South African soldiers, personnel carriers, attack helicopters and mortar units rumbled across the border at dawn Tuesday after the government had asked regional countries to send military help.

The action follows weeks of opposition party demonstrations over allegations of election-rigging in May, as well as an army rebellion that had effectively paralyzed the government.

Lesotho (pronounced leh-SOO-too), an impoverished kingdom slightly smaller than Maryland with a population of 2 million people, is surrounded by South African territory and is largely dependent on South Africa for jobs and income.

Officials said the South African force had secured Lesotho military headquarters, the main air force base, central business district and a neighborhood where most diplomats and Cabinet members live.

During the intervention, angry crowds looted stores, stoned cars and set government buildings and shopping centers ablaze. Foreign Minister Tom Thabane said a bazooka attack destroyed his house.

At least 10 South African soldiers died in a firefight outside outside Makoanyne barracks northeast of the capital, a senior South African officer, speaking on condition of anonymity, told The Associated Press. Five Lesotho citizens were also reported killed.

Military officials in South Africa also reported that five soldiers were killed in sometimes fierce fighting and sniper fire throughout the capital, which has been gripped by weeks of anarchy. It was not clear whether these casualties were among the 10 in the barracks.

``We didn't expect them to be so hostile,'' the senior officer said about the Lesotho rebels, adding that the South African force lacked enough troops and proper equipment to handle the stiff resistance.

The South African troops were unable to contain looting and street violence because they were concentrating on securing the bases, where they were drawing ``a lot of fire,'' said Lt. Col. Laverne Machine, a South African Air Force spokesman.

``We'd hoped it would be peaceful,'' she said of the intervention.

An Associated Press reporter and photographer as well as a BBC cameraman were pinned down for hours at the Makoanyne barracks near the airport, where South African armored vehicles were forced to retreat.

Freelance photographer Greg Marinovich, a Pulitzer prize-winner for The Associated Press, also was shot in the leg by a sniper in another incident and was evacuated to South Africa. A South African Broadcasting Corporation cameraman was injured as well.

About 200 troops from Botswana had arrived at the Lesotho-South African border, witnesses said. They were to join the 600 South African troops, the South African military said.

South African troops met strong resistance in the morning securing the royal palace, where Prime Minister Mosisili charged that King Letsie III has harbored opposition activists.

American citizens were told to stay indoors and South African embassy employees were evacuated. Hundreds of foreigners were fleeing to South Africa, but some were refused admission because they lacked South African visas.

The decision to send troops into Lesotho has drawn criticism from South African opposition parties, churches and civilian organizations.

Since the fall of white rule in 1994, South Africa has pursued a non-interventionist policy until Tuesday.

Under apartheid, the nation's rulers sent troops across its borders to countries that included Angola and Namibia to take part in wars and to pursue government opponents, particularly in Lesotho and Botswana.

The mobilization caps weeks of unrest by opposition demonstrators who claim May elections swept by the Lesotho Congress Party were rigged.

The Congress party won 79 of 80 seats but scored only 61 percent of the vote.