Angola said yesterday that a 3,000-strong South African fighting force had occupied several towns in the south of the country and killed more than 300 civilians.

A Defense Ministry statement issued in Luanda said the force invaded Angola on June 7 by crossing the southern border with South African-controlled Namibia (South-West Africa).

Asked about the Angolan announcement, a South African defense spokesman merely noted that Prime Minister Pieter W. Botha told parliament June 13 that South African forces had conducted a major raid against guerrilla bases in southern Angola, killing 200 guerrillas and losing 16 of their own men.

The South African defense department confirmed an Angolan report that Angolan forces shot down a South African helicopter Monday and killed a crew member.

The Angolan news agency ANGOP, in a telexed report to Reuter news agency, said the South African fighting force consisted of three infantry battalions and one unit of paratroopers backed by three squadrons of Mirage fighters, two Hercules C130 transport planes, 20 Puma helicopters, 32 pieces of artillery and 40 armored cars.

ANGOP said more than 300 civilians, including old men, women and children, had been killed and that seven military personnel had died.

The Angolan Defense Ministry said the force was still operating in southern Angola.

The U.N. Security Council convened after Angola requested an "urgent and immediate" meeting on the charges, and seven Third World nations introduced a resolution condemning South Africa.

A South African defense spokesman said he had "nothing to add" to the speech by Bothadisclosing the assault aimed at guerrillas of the South-West African People's Organization, fighting for independence for Namibia.

Botha said then that wherever SWAPO established bases "we will track them down again and destroy them again," implying that further raids would be made if necessary. It is known that South African troops operate in Angola almost daily.

The South African defense department, confirming the Angolan government's report that it had shot down a South African helicopter, said Angolan forces attacked the crew after it was downed, killing one member.The pilot escaped and made his way back into Namibia.

The helicopter was shot down Monday as it landed troops near Kangongo in Cunene province, Angola, the South Africans said.

South Africa has tried to avoid getting involved in a direct confrontation with Angolan forces in their fighting against SWAPO.