Some 70,000 construction workers in South Africa have gone on strike, halting work on stadiums being built for the 2010 World Cup.

Unions are threatening to wreck the tournament if their demands for a 13% wage increase are not met.

Organisers say they are confident the grounds will still be ready, unless the strike continues for months.

Union organiser Patrick Geqeza blamed management inflexibility for precipitating the strike.

"We feel bad about going on strike. [But] they don't want to meet us half way," he told AP news agency.

At present most of the workers are being paid 2,500 rand ($310; £192) a month