They are also on a heightened state of alert as were all US embassies and consulates around the world, said embassy spokeswoman DeAngela Burns-Wallace.

She would not elaborate on the reasons behind the decision to close US missions in South Africa for the day, but said it was not directly linked to countrywide protests against the start of a US-led war on Iraq.

The US has an embassy in Pretoria and consulates in Johannesburg, Cape Town and Durban.

A group of about 30 people outside the consulate in Johannesburg carried placards and shouted "No blood for oil."

Burns-Wallace said a number has been left on all answering machines for American citizens to phone in case of an emergency.

Details of when the missions are to reopen would be posted on the embassy's website shortly, she added.

US officials were working closely with the South African government and police service on matters of security.

American citizens in the country had been advised to stay alert and register with their nearest consulate, Burns-Wallace said.

The British government buildings in South Africa remained open for business as usual, said spokesman Nick Sheppard. Staff members were on alert and a high state of vigilance.

"Although there is an increased state of vigilance around the world, I am not aware of any specific threat against British interests or nationals in South Africa," he added.

(Xinhua News Agency March 20, 2003)