JOHANNESBURG, Dec. 15— The South African Army reported tonight that six people were killed and five people seriously wounded when a light truck set off a land mine close to the border with Zimbabwe.
An army spokesman in Pretoria said those killed were members of two families, including a mother and two children. The incident occurred at about 6:50 P.M. at the Chatsworth game farm, about 19 miles from the border town of Messina.
The incident brings to seven the number of land-mine explosions in less than three weeks near Messina. A black farm laborer was killed and six people, four of them soldiers, were wounded in explosions late last month. A soldier was slightly wounded on Thursday when an army troop carrier set off a land mine during security operations being carried out because of the series of explosions.
The army spokesman said the mine that exploded today was planted at the same time as all the others. Soldiers have found and defused four other land mines in the area and have maintained daily patrols along the border with Zimbabwe.
First Such Explosions
After the initial land-mine explosions, the first in South African territory, army officers said they had been told by farmworkers that three black men had been seen climbing a wire and sisal border fence to cross the Limpopo River into Zimbabwe. The South African Army said the three men were presumed to be ''terrorists'' from the outlawed African National Congress, which is seeking to overthrow the white minority Government in South African. The army said the men were presumed to have been returning to Zimbabwe after having planted the mines.
The South African Government immediately warned black-ruled Zimbabe that its troops would ''follow the tracks'' of the insurgents into the neighboring country unless Zimbabwe assured Pretoria that it would not allow its land to be used for the planning and execution of violence against South Africa.
Prime Minister Robert Mugabe said he would not allow Zimbabwean territory to be used for such acts. He later charged that South African troops were massing along the border, apparently in preparation for an invasion, and that Zimbabwe was prepared to repel any invasion. The Government dismissed Mr. Mugabe's statements.
Last week South Africa's Minister of Defense repeated his warning, saying the army would seek out guerrillas wherever they were hiding.
Other Bombings by Rebels
The exiled African National Congress, which has its headquarters in Lusaka, Zambia, has taken responsibility for placing many bombs in South Africa, killing as many as 19 people at a time. But an army spokesmen said at the time of the initial land-mine explosion in November that it was the first of its kind in the country.
Army officers have said the land mines planted near the northern border were Czechoslovak devices of a type first used by Zimbabwean guerrillas in their war against white rule in what was then called Rhodesia.
The army spokesman said tonight that the wounded included the owner of the game farm and his wife and daughter. Both of the families were from the town of Tzaneen. He said that the army had no idea how many land mines might still be in the area but that normal operations were continuing to insure the area's security.
The army appealed to visitors to the area not to drive ''around aimlessly'' and to report to military headquarters before going there.
A number of game farms in the area are not regularly inhabited. The security forces have been first checking for the explosives in farms that are occupied.
Cameraman in Hospital
In other developments, a television cameraman who was shot in the leg by the police on Saturday while filming a peaceful funeral procession in the black township of Mamelodi, near Pretoria, underwent surgery Saturday night and was expected to remain in the hospital for as long as a week, according to the journalist's friends.
Brian Tilley, the freelance cameraman who was filming the event for Dutch television, was set upon by the police in an apparently unprovoked attach. One of his legs was reportedly shattered below the knee by the shotgun blast.
Other cameramen and soundmen working for foreign news organizations, including CBS News, were also manhandled by the police and taken to a police station at gunpoint, where they were briefly detained.
The incident occurred after two policemen spotted the journalists filming the funeral march and rushed toward them through the crowd. Angry mourners came to the journalists' defense by throwing stones at the policemen, one of which may have inadvertently hit Mr. Tilley, 29 years old, in the leg.
The police said on Saturday that the journalists had accompanied the police to the station ''of their own free will'' and that they had been well treated. The polcie reported only that one correspondent had been injured by stone-throwers.
The Foreign Correspondents Association condemned the attack on Mr. Tilley and the others as ''unprovoked harassment'' at a peaceful event. Mamelodi is not covered under the state of emergency and the press restrictions imposed last month.