Rioting dockers clashed with police at the European Parliament on Monday as strikes disrupted Europe's main ports in protest at European Union plans to throw open port services to greater competition, according to Reuters. In Strasbourg, where the EU legislature is due to debate a bill that would end union-backed monopolies on port labour, protestors burned cars in the city centre and smashed some of the parliament building's outer windows with rocks and ice. Police fired water cannon and tear gas into the crowd after a few hundred from a throng of 10,000 union members turned violent, a police spokesman said. He said 12 policemen were injured, one suffering serious head wounds. "There were a few incidents earlier in the day in Strasbourg in which a number of vehicles were burned. We now fear there could be a repeat of this, this evening when the official demonstration is over," one policeman said. In Europe's busiest port, Rotterdam, 600 dockers joined a four-hour strike affecting work at several container, bulk and ferry terminals, a spokesman for the biggest Dutch trade union FNV said. No oil terminals were affected at Rotterdam, where the protest ended in mid-afternoon, port officials said. The port of Antwerp in neighbouring Belgium, Europe's second biggest by volume, was at a standstill. Parliament is due to debate the legislation liberalising port services across the 25-nation bloc, strongly backed by employers, on Tuesday with a vote due on Wednesday.