The Democratic Alliance and Zimbabwean civic groups have expressed their outrage at South Africa's sale of helicopter spares to Zimbabwe.
Zimbabwean Air Force Alouette helicopters hovered over Harare on Tuesday in a show of force ahead of a two-day strike which is due to begin on Thursday.
Zimbabwe turned to South Africa for the spare parts after France, where the helicopters were initially acquired, refused to sell the parts because of the European Union arms embargo on the Mugabe government.
Zimbabwe's main opposition party, the Movement for Democratic Change, said the sale confirmed what it had always said: "South Africa is aiding and abetting the Mugabe regime in its systematic destruction of Zimbabwe.
"We have a regime that goes on buying sprees of arms and their spares in China and South Africa when its people are starving and it has no fuel," said MDC secretary-general Welshman Ncube.
"South Africa obviously sees nothing wrong in how Mugabe abuses the security forces against the nation."
Democratic Alliance defence spokesperson Rafiek Shah said it was morally outrageous for Armscor to sell spare helicopter parts to replenish the armoury of a country that was virtually waging war "against its own defenceless citizens".
"What message are we sending to the international community if President Thabo Mbeki's government keeps on allowing South African institutions to aid a thoroughly discredited regime like President Robert Mugabe's?" Shah asked.
Armscor spokesperson Bertus Celliers confirmed the sale in an interview with Independent Newspapers on Tuesday.
An Afrikaans daily had originally reported the story.
Celliers stressed that Armscor had sold only spare parts and not entire Alouette helicopters.
The spares included rotor blades, windscreens "and other such similar parts", he said.
The sale was concluded in March.
Celliers said the sale was not in contravention of the National Conventional Arms Control Committee, which must issue prior authorisation for any sales of military equipment abroad. NCACC regulations did not prevent the sale of spare military parts, he said.
Zimbabwean National Constitutional Assembly spokesperson Lovemore Madhuku, who is spokesperson of the alliance calling for Thursday's strike, said Armscor should come and see the Alouettes at work against innocent civilians "whose only crime would be to try and stage peaceful protests".
"When they (Armscor) see people being brutally beaten during the strike on Thursday and Friday, they should know they have played a crucial role in strengthening Mugabe's hand. They should feel happy for their efforts," he said.
Zimbabwe normally uses its Alouettes to co-ordinate the efforts of security forces in crushing protests during demonstrations. Teargas is also fired from the air.
Zimbabwe's helicopter squadron has been effectively grounded after being damaged in the Democratic Republic of Congo and hampered by poor maintenance because of the lack of spare parts. But South Africa's help will ensure the squadron is airborne.
As the strike to protest against Mugabe's "senseless repression" looms, Zimbabwean police spokesperson Wayne Bvudzijena vowed that the police would deal ruthlessly with anyone participating in the protests.
The protests were called to highlight the plight of more than 22 000 arrested informal traders and the destruction of informal settlements that has left thousands homeless. - Independent Foreign Service