Police tried to disperse crowds demonstrating against a new Internet law using water cannon and tear gas in the central commercial district in Istanbul.
Police shut down Istiklal Street, the main pedestrian street in central Istanbul, as well as Gezi Park, the site of anti-government protests last June.
Police fired plastic pellets and tear gas and used water cannon to disperse the protesters. Some protesters set off fireworks and threw bottles and stones at the police.
The demonstration was organized over Facebook and Twitter against a proposed Internet law that passed Turkish parliament earlier this week but still awaits presidential approval. Critics of the law say it will greatly limit Internet freedoms while the government says the law is mainly to prevent child pornography and personal privacy.
The government of Turkish Prime Minister Recep Tayyip Erdogan has been facing a corruption probe since mid-December.
But evidence against the prime minister's close circle has been leaked online. Critics warn that the Internet bill is an attempt by Erdogan to block evidence damning to his government.