South African authorities are urging World Cup visitors to be extra careful following a spate of robberies targeting foreign journalists and players ahead of the opening match.

Several Chinese journalists were mugged in the centre of Johannesburg on Wednesday, the same day armed men robbed three foreign journalists in the country's northwest region. Three members of the Greek team said money was stolen from their hotel rooms.

South Africa has one of the world's highest rates of violent crime, and the thefts were a reminder of dangers that face hundreds of thousands of fans coming to watch the month-long tournament.

The government sought to provide reassurance, saying it has 190,000 policemen on duty, including at least 40,000 assigned to the World Cup.

A joint operations centre led by police and including military, intelligence and other government agencies is supervising the games' security from an undisclosed location.

Large sporting events like the World Cup, which are watched by hundreds of millions around the globe, have been targeted by troublemakers, crime gangs and militants in the past.

In 1972, Palestinian gunmen took hostage athletes and coaches from Israel's Olympic team, killing 11.

'Heightened risk'

The U.S. State Department has warned that there is a "heightened risk that extremist groups will conduct terrorist acts within South Africa in the near future."

But Danny Jordaan, chief executive of the local organizing committee, said he was "comfortable" with the level of security, and authorities have said they are ready not only for petty crime but also for any of the hooliganism that has been a problem in some past World Cups.

"Policing of the country and ensuring the safety and security of all within it remains a 24-hour operation," said Themba Maseko, a government spokesman. "Those in distress are requested to report to relevant authorities and the appropriate assistance will be rendered."

So far, only thefts and robberies have been reported.

FIFA spokesman Wolfgang Eichler confirmed the mugging of a group of Chinese journalists on a downtown Johannesburg street.

A Chinese media report said four journalists were held up by armed men and robbed of cash and a camera.

Three more robbed

Early Wednesday, thieves sneaked into Nutbush Boma Lodge outside Magaliesburg, 75 miles northwest of Johannesburg, and robbed three journalists (two from Portugal, one from Spain) of money, camera equipment, laptop computers and mobile phones. Police said three suspects were arrested and some of the property was returned to the victims.

In a sign of the sensitivity around the crime problem, South Africa's top police commander, Gen. Bheki Cele, met with Spanish and Portuguese journalists in Magaliesburg, promising regular helicopter and surveillance aircraft sweeps of the areas, as well as additional resources to ensure their safety.

Three Greek players had money stolen from their hotel rooms at the beach resort of Umhlanga Rocks near Durban on Tuesday, said Lt.-Col. Leon Engelbrecht of the South African police.

The unidentified players reported $1,900 US was stolen from their rooms at the Beverly Hills Hotel, Engelbrecht said. He said the Greek team told police it did not want to open a case.

Anneli Botha, a former South African police officer now with the Institute for Security Studies, an independent South African think-tank, said any crimes related to the World Cup were likely to draw attention.

"Each and every robbery is going to reach the headlines," she said. "You'd travel to anywhere else in the world, and report this to the police, and that's not going to happen. There's tremendous attention because of the World Cup."

Unrelated to the tournament, three British nationals, two women and a man, who were part of a school group touring South Africa, were killed in a bus crash on Thursday, police said.

Provincial police spokesman Capt. Leonard Hlathi said the vehicle was carrying 22 people, including 18 British students and two teachers, when it veered off the road near the town of Barberton, just outside the World Cup host city, Nelspruit, in northeast South Africa.