UPDATE 4-Thousands strike at S.African phone group Telkom

* Thousands of Telkom workers strike, picket offices

* Metalworkers threaten "radical measures" against Eskom

(Adds NUMSA spokesman, analyst)

By Michael Georgy

JOHANNESBURG, Aug 3 (Reuters) - Thousands of workers at South African telephone group Telkom (TKGJ.J) began striking on Monday, the Communications Workers Union said, in the latest industrial action to hit the country during the recession.

The protest at Telkom, Africa's biggest fixed-line phone operator, began only days after the end of a five-day strike by tens of thousands of council workers that saw rubbish pile up on the streets and key services paralysed.

Unions, including those in the critical mining sector that could have caused the most economic damage, reached a wage agreement last week.

The Communication Workers Union (CWU), representing 44,000 workers, said that more than 3,500 Telkom workers in four of South Africa's nine provinces began the two-day strike to push demands for pay increases.

"We expect that quite a sizable number of our members will heed the call for a stayaway," CWU General-Secretary Gallant Roberts told Reuters.

He said workers picketed Telkom offices in four provinces.

The wave of strikes in South Africa has challenged President Jacob Zuma's economic policies over the past month, as the unions that helped bring him to power in April elections flexed their muscles, seeking a payback for their support.

Most of the pay disputes have been settled, but the unions' success in securing wage rises could encourage more industrial action.

"Every time a settlement is reached above the inflation figure clearly it encourages other unions to go for the higher percentage. So, there can be very little doubt about that," Executive Research Associates analyst Nel Marais said.

METALWORKERS THREAT

South Africa's National Union of Metalworkers (NUMSA) threatened "radical measures" if state power utility Eskom [ESCJ.UL] did not meet its wage demands.

"This might include pulling off the plug and unleashing a blackout if need be. But we do not want to get to that point although Eskom is pushing us to that direction," NUMSA said in a statement.

NUMSA spokesman Castro Ngobese said the union will take those measures if Eskom does not concede by the end of this week.

Zuma is in a difficult position. He is indebted to unions that are a crucial part of his support base, but raising government spending could worry foreign investors in the midst of South Africa's first recession since 1992.

To end the council strike, officials agreed a 13 percent pay rise, just below the 15 percent demanded by the unions and almost double the inflation rate.

Further double-digit pay settlements in the private and public sectors would put added strain on Africa's biggest economy, compounding the impact of a 31.3 percent increase in electricity prices last month which drove inflation higher.

Pressure on the government has also come from township residents, who have demonstrated to back demands for better living conditions for millions of blacks who lack adequate housing, electricity and water 15 years after the end of apartheid. (Additional reporting by Alison Raymond; editing by Michael Roddy)