JOHANNESBURG - South African President Jacob Zuma said police will move swiftly to crack down on rioters after violent protests erupted this week over poor services and jobs.

Zuma told businessmen late Thursday that although the government acknowledged problems with delivering basic services, looting, violence and the destruction of property cannot be justified.

The crisis is an early test for Zuma, who took office in May after pledging to do more to help the poor. Financial woes in Africa's biggest economy have limited his ability to carry out that main plank of his party's election manifesto.

Police fired rubber bullets and tear gas Wednesday at township rioters calling for the removal of African National Congress local officials who they accuse of corruption. Scores of protesters have been arrested.

There can be no justification for violence, looting and destruction of property or attacks on foreign nationals residing in our country, Zuma said.

The law enforcement agencies will continue to act swiftly and to take action against all who break the law. They have our full support as they carry out their mandate to maintain law and order in our communities.

The protests come as the government faces pressure from workers threatening strikes to back demands for higher wages.

A fuel sector union agreed to an improved 9.5 percent wage offer Thursday but warned it may yet strike in sympathy with paper and chemical workers who downed tools this week.

Council workers are threatening to stay at home from Monday, action that could keep tens of thousands of local government employees at home, crippling the public sector. Gold and coal unions are considering a pay offer. If they reject it stoppages will hit some of the world's biggest mines.

Zuma said economic conditions could make this year's wage talks more complicated.

Due to the current economic conditions, these negotiations may be more difficult this year. Employers and workers must negotiate in good faith and should be prepared to understand each other's positions, he said.

Police said calm had returned to Siyathemba township, southeast of Johannesburg, after four days of protests. Violence had spread to other townships around Johannesburg.

The scenes were reminiscent of attacks on foreigners last year that killed 62 people, and dented South Africa's image less than a year before it hosts the soccer World Cup.

(Editing by Louise Ireland and Marius Bosch)