Ten persons were reported killed today as violence erupted in a previously placid black rural region of South Africa that the government has forcibly annexed to a tribal "homeland" scheduled for nominal independence later this year.

The fighting broke out as crowds of demonstrators in the region, called Moutse, clashed with officials of the "homeland" and rioted in protest of the incorporation, which took effect today.

Police said three other blacks died in incidents of racial violence throughout South Africa today, for a total of 13 deaths on the first day of 1986, while 10 blacks were reported wounded by police fire after a crowd estimated at 5,000 marched onto an Indians-only beach in Durban.

The Durban crowd, which had spilled over from a jammed blacks-only beach, burned a police car and stoned other vehicles on a beachfront highway before it was brought under control, police said.

Two of today's deaths came when government officials fired at crowds that attacked the officials' homes in the central Cape Province towns of Upington and Jansenville, a police report said.

Another man was killed when police opened fire on a crowd that attacked them in Bonteheuvel, in western Cape Province, the report added.

Details of what happened in Moutse are sketchy, but police reports said mobs set fire to vehicles and fighting broke out in three locations between people from the incorporated area and the homelanders. Police reported five dead.

A civil rights worker who knows the area well said in a telephone interview tonight that at least another five had died, adding that the casualty figure could be much higher, as the fighting appeared to have been widespread and was continuing.

Civil rights workers had predicted violence in the area if the incorporation went ahead in the face of fierce resistance by Moutse's 120,000 inhabitants.

Moutse is about 70 miles north of Pretoria and consists of three pockets of land totaling about 65 square miles. Most of its inhabitants are deeply conservative peasant farmers of the small Pedi tribe who have been there for at least two centuries.

Because the Pedi are a minor tribe who do not fit easily into the Pretoria government's apartheid, or "separate development," scheme of partitioning South Africa into 10 "homelands" for each of the major black tribes, leaving the white minority as the dominant element in the remaining 87 percent of the country, they were first attached to the North Sotho tribal "homeland" of Lebowa.

Although modern black nationalists oppose any aspect of the "homelands" policy, the conservative people of Moutse seemed content with this arrangement, particularly as Lebowa's tribal leaders opposed the policy's ultimate aim of seeking nominal independence from South Africa.

Independence threatens the citizenship and other rights of the black people involved, but can mean highly paid prestige jobs for the black politicians who accept it.

Four years ago Moutse was removed from Lebowa, and last August Pretoria announced that it was to be incorporated in a newly created "homeland" called KwaNdebele whose leader, Simon Skosana, has agreed to independence.

KwaNdebele was created in 1980 out of 16 farms that the government bought from whites in northern Transvaal Province. It is intended as the "homeland" for the small Ndebele tribe, an offshoot of the Zulus of Natal Province who plundered the Transvaal during the 19th century before being driven by white pioneer armies into what is today Zimbabwe, where they form the basis of opposition leader Joshua Nkomo's support.

Only a few scattered groups of Ndebeles remained in South Africa. Historians contend there is no territory that can be considered their traditional homeland, and that KwaNdebele has been artificially created to fit the apartheid ideology. KwaNdebele's main feature is a chain of resettlement camps to which an estimated 200,000 blacks have been sent from the cities and towns of the Transvaal under the country's strict influx control regulations. They have more than doubled the area's original population. Few are Ndebeles.

Apart from the resettlement camps the "homeland" has only one town, Siyabuswa, especially built as a capital. It has a legislative assembly, government offices, a school, a teachers' training college and a few business establishments, most of which belong to members of the "homeland" Cabinet.

Despite its shortcomings, Chief Minister Skosana, a one-time vegetable seller who failed to complete primary school, has accepted independence for KwaNdebele, an arrangement that is scheduled to be formalized this year.

Moutse, by contrast, is a less overcrowded and better developed area. It has a 360-bed hospital, 60 schools, a telecommunications system and tarred roads.

Joanne Yawitch, a member of a civil rights group that has worked extensively in the area, said she believes Moutse's superior infrastructure is the reason it is to be incorporated in KwaNdebele. It will give the intended independent state a semblance of viability, she said.

"It will double KwaNdebele's size and infrastructure," Yawitch said in an interview.

"It is the homeland's reward for accepting independence. That is why the government has ignored the opposition of the Moutse people."

People interviewed recently in Moutse said they opposed joining KwaNdebele because they would lose their South African citizenship and other rights when it became independent.

Some people said they feared the Ndebele tribal courts, which mete out corporal punishment and enforced circumcision for men and women.

Others said they opposed the KwaNdebele voting system, which excludes women, and feared the loss of business rights and discrimination against their language.