Most of London's buses have been halted by a one-day strike by workers demanding a bonus for working during the Olympics.

The staff says it wants a 500 pound ($780) premium for working during the 2012 London Olympic and Paralympic Games.

On Thursday a High Court judge granted an injunction stopping a strike by workers at three bus companies, citing balloting irregularities. But staff at 17 other bus firms walked out. Transport for London, the city's transit operator, said only 24 percent of buses were running on the network, which usually carries 6 million passengers a day.

The bus workers are the latest transit staff to demand extra money to work during the games. London's subway train drivers have already secured one-time payments of 500 pounds.

The Olympics run from July 27 to Aug. 12.