Johannesburg — ZIMBABWE'S main opposition Movement for Democratic Change (MDC) faction, led by unionist Morgan Tsvangirai, has vowed to launch its 2008 presidential election campaign on Sunday despite police attempts to block the rally.

Fearing the rally could be a platform for Tsvangirai to instigate mass antigovernment protests, police have withheld permission to hold the gathering.

Tsvangirai and Arthur Mutambara, who leads the other faction of the MDC, have threatened a nationwide defiance campaign against President Robert Mugabe's regime.

Police efforts to prevent Tsvangirai's rally in the capital, Harare, follows a clampdown on widespread strikes and dissent.

In the latest of hundreds of arrests over the past two weeks, Progressive Teachers' Union of Zimbabwe president Raymond Majongwe and two other unionists were detained in Harare and have been charged under the Public Order and Security Act with inciting more teachers to strike. They were demanding adequate wages.

"(Low wages are) degrading and inhumane to teachers ... as long as teachers, and other workers of Zimbabwe, including the army and police are not earning equated wages, strike action will characterise 2007," the Zimbabwe Congress of Trade Unions (ZCTU) said.

The Congress of South African Trade Unions (Cosatu) yesterday condemned the arrests. "We agree fully with ZCTU that the arrests are a violation of human rights, as teachers are allowed to go on strike," said Cosatu spokesman Patrick Craven.

Zimonline reported yesterday that Mugabe's government had called in the military to force striking teachers to return to work by intimidation and threatening to withhold their pay. Several school heads on Wednesday said they had been summoned to provincial head offices where senior education officials and army officers ordered them to force teachers to call off the strike.

The teachers union confirmed striking teachers were being intimidated by the military.

At least 174 members of the activist group Women of Zimbabwe Arise (Woza) and a related organisation, Men of Zimbabwe Arise, remained in custody yesterday. Police arrested 284 Woza members in Harare and Bulawayo on Tuesday.

An estimated 1300 members of the groups had demonstrated against the deteriorating economy and intensifying political crisis, said the Voice of America on Wednesday.

Several student union representatives were in custody this week after protesting against a 2000% increase in fees.

Zimbabwe's inflation has topped 1600%, the highest in the world.