Pretoria - The men arrested aboard a captured plane in Zimbabwe are all former South African Defence Force (SADF) soldiers from Unit 32, based in Namibia, a South African diplomatic source said on Wednesday.

The source told Sapa that the plane had indeed been transporting mercenaries to Equatorial Guinea, and it stopped over in Zimbabwe to pick up weapons from a military depot.

Beeld alleges that the weapons were manufactured by Zimbabwe Defence Industries (ZDI), which it alleges was paid $180 000 (about R1,2-million) for the weapons.

"So I suppose you could say there were no weapons on the plane before it got to Zimbabwe," the source said.

Sixty-four men, including 20 South Africans, 18 Namibians, 23 Angolans, two DRC citizens and a Zimbabwean travelling on a South African passport have been arrested and are in prison in Zimbabwe.

The Boeing 727-100 was detained by Harare on Sunday after airport authorities became suspicious of the pilot's reported claim that the plane was only carrying three crew and four cargo handlers.

South African Foreign Affairs Minister Nkosozana Dlamini-Zuma said on her arrival back from India that her department was in no rush to assist the South Africans in Zimbabwe, or another group which is under house arrest in Equatorial Guinea.

"They are not exactly innocent travellers finding themselves in a difficult situation," she said.

However foreign affairs officials would find out what extradition treaties, if any, were in place.

She said the department was still trying to establish what was going on but that "indeed there was a link between the plane and Equatorial Guinea".

She confirmed there were at least seven South Africans who had been arrested in Equatorial Guinea and that one had "spilled the beans".

"I know one man has addressed the diplomatic corps and explained what funny things they were doing up there," she said.

Dlamini-Zuma said government was concerned that South Africans were involved in mercenary activities.

"We don't like the idea that South Africa has become a cesspool of mercenaries," she said.

Equatorial Guinea's Information Minister Agustin Nse Nfumu said on Tuesday his government had detained 15 suspected mercenaries, and declared they were an "advance party" for the group of 64 on board the impounded aircraft.

He said the leader of the group, a white South African called "Mick", had confessed to a plot to kill the president.

But Charles Burrow, a senior executive at Logo logistics - the plane's owner - maintains its all a "dreadful misunderstanding".

Burrow insists the alleged mercenaries were security guards en route to various mining operations in the Democratic Republic of Congo and the alleged weapons were bits of mining equipment. - Sapa