By Bate Felix

JOHANNESBURG, Jun 11 (Reuters) South Africa's powerful COSATU trade union warned today that a crippling civil service strike could ''turn violent'' if its pay demands were not met.

The public sector workers' strike, which began on June 1, has crippled government hospitals and schools across the country, and unions say a new government offer of a 7.25 per cent wage increase was not enough.

''Workers will be soon angry, they will be frustrated, and they will see anybody going to work, irrespective of how genuine their reasons are, as basically betraying their cause,'' SAPA news agency quoted COSATU general-secretary Zwelenzima Vavi as saying.

Speaking to the Police and Prisons Civil Rights Union national congress in Cape Town, he said: ''And very soon the strike will turn violent.'' But the tough talk was accompanied by an offer to return to the negotiating table.

COSATU has revised its demand for a 12 percent wage rise to 10 per cent.

South Africa's government vowed yesterday to press ahead with firing essential workers striking for higher pay despite being barred by law, a move denounced as provocative by labour unions.

They have begun receiving dismissal letters, SAPA reported.

The labour strife has dented some essential services, with members of the public complaining that they cannot get through to government workers.

A domestic worker in KwaZulu-Natal province was told ''there were no workers and there was nobody at the hospitals'' when she called an emergency number in a bid to save her pregnant daughter's life, SAPA reported.

Public Service and Administration Minister Geraldine Fraser-Moleketi said the number of striking employees had gradually declined, but there were increasing reports of intimidation against those wanting to return to work.

The government has deployed soldiers to help doctors tend to patients at some hospitals.

Finance Minister Trevor Manuel has said the government had not worked out the financial cost of the strike, but added that it had hit the poor without access to private health care.

COSATU, a crucial part of an alliance with the ruling African National Congress, has accused President Thabo Mbeki of promoting the interests of big business and neglecting poor workers, an allegation he denies.

REUTERS DS HT2312