Police fired rubber bullets and stun grenades to break up a protest by hundreds of stadium staff unhappy at their wages in the first major unrest of the football World Cup.

As organisers promised to investigate why thousands of seats were empty at weekend matches, they also struggled to contain a backlash against the din generated by the vuvuzela horns which have become the symbol of the tournament.

Danny Jordaan, chairman of the local organising committee, said he would consider banning the horns if they drowned out national anthems although a spokesman later said they were here to stay.

The protests in Durban broke out around midnight after the match between Germany and Australia as around 400 stadium staff protested what they said was a pay cut from 250 rand ($A39) to 190 ($A30) per day outside the main gate.

"They were unhappy about the wages they were getting from their employers, so they started getting unruly," police spokeswoman Phindile Radebe told AFP on Monday.

Police broke up the protest at the stadium, but about 200 continued protesting on a nearby street, where rubber bullets and stun grenades were fired to break up the demonstration, she said.

"No one has been arrested so far," she said, adding that fans had already left the stadium when the protest broke out.

A spokesman for the local organising committee said a meeting was being set up between the firm contracted to provide stewarding and workers to ensure the dispute can be resolved, insisting spectators' safety had not been in danger.

"There was an internal dispute between the security company employed by the organising committee and some of their static security stewards," Rich Mkhondo told reporters.

"This is an internal matter and we have convened a meeting between the representatives of the stewards and the service provider and ourselves to make sure things are ironed out and that we will not see a repeat of what happened this morning."

The tournament also faced negative headlines over ranks of empty seats which were spotted at some of the less glamorous ties over the weekend.

Around 8000 seats were empty during Saturday's match between South Korea and Greece while there were also gaping holes at Sunday's game between Slovenia and Algeria in the northern city of Polokwane.

Most of the empty seats had been sold to corporate clients who had just not turned up.

"Of course it is not nice to see empty at a World Cup stadium," said FIFA spokesman Nicolas Maingot.

"You cannot draw conclusions after eight games."

Another FIFA official meanwhile ruled out any possibility of the vuvuzelas being shown the red card.

"Vuvuzelas will not be banned from the stadiums," said Stan Schaffner.

His comments served as a slapdown to LOC chairman Danny Jordaan who said in a weekend interview he would consider a ban "if there are grounds to do so".

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