A partial strike by bus drivers in Rio demanding a 40 percent wage hike on Thursday saw 325 vehicles damaged, with some set ablaze, a union leader opposed to the stoppage said. Union vice-president Sebastiao Jose da Silva said only some 20 percent of services had been cancelled in the 24-hour stoppage but indicated strikers had damaged the vehicles, throwing stones and even setting fire to some. The stoppage came just 37 days before hundreds of thousands of domestic and foreign tourists are set to flood into Rio for the World Cup. The city will host seven matches, including the July 13 final. Wednesday saw federal police go on strike in several Brazilian cities, including the capital Brasilia, and threaten to do so again during the tournament. A group of police held a peaceful protest in Rio just as the Brazilian World Cup squad was being unveiled. Unions and the privately-run bus companies reached a wages settlement in March, agreeing to double figure rises. The agreement also put an end to drivers also having to work as conductors, Da Silva said. But the drivers want to see typical salaries rise further to around 2,500 reais ($1,100) a month. Da Silva suggested there was a political motive to put pressure on the government in an election year. Strike leader Helio Teodoro told CBN radio the strike was not political. He added the movement was "peaceful" and had the backing of other unions -- though he criticized violence. Pickets blocked several western access roads into Rio, posing a headache for thousands of commuters into the city. Trains were packed as they sought to find alternative transport.