Trade union federation Cosatu has warned of mass strikes in response to the NPA's decision to appeal against the Pietermaritzburg High Court ruling on ANC President Jacob Zuma.

Cosatu's KwaZulu-Natal secretary Zet Luzipho said at a media briefing in Durban on Wednesday: "The fact that NPA wants to continue this case... is a declaration of war on our people."

He said each time the authority took Zuma to court, the masses would strike. "And it won't only be on the day of the court case, but also before he goes to court," Luzipho added.

The National Prosecuting Authority (NPA) on Wednesday said it had studied Judge Chris Nicholson's judgment declaring Zuma's prosecution invalid, and had taken senior counsel's advice.

"Consequently, we have decided to apply for leave to appeal against the judgment."

It added: "The NPA has yet to make a decision on whether to recharge Mr Zuma."

Zuma faced 16 charges which included racketeering, corruption and fraud, while French arms company Thint faced charges of racketeering, corruption and money laundering.

Nicholson made several pronouncements on the independence of the prosecuting authority and agreed with Zuma that there was some merit in his claims of a political conspiracy linked to the investigation against him for allegedly receiving bribes from Thint.

Sapa