Thousands of protesters are marching at the Earth Summit in the South African city of Johannesburg to demand action on poverty and the environment.

Between five and 10,000 demonstrators set out from South Africa's poorest township, Alexandra, for the eight kilometer march to the fashionable Johannesburg suburb of Sandton, where the United Nations conference is taking place.

Most of the protesters are poor South Africans, demanding land and poverty relief. But they have been joined by militant anti-globalization activists, AIDS victims and several hundred pro-Palestinian lobbyists.

Thousands of South African police officers, some in armored vehicles with mounted machine guns, are deployed to protect the summit venue.

Officials have vowed to crack down on illegal protests and prevent violence that has disrupted large international meetings in recent years.

Meanwhile, delegates at the Earth Summit are continuing negotiations, hoping to prepare a conference document in time for the arrival of more than 100 world leaders Monday. Unresolved issues include agricultural subsidies, renewable energy resources and access to clean water.

The focus of the summit is on forging accords on reducing poverty while protecting the planet's environment.

The 10-day summit in Johannesburg is a follow-up to the Rio de Janeiro summit in 1992.