Up to 100 people have been injured in the clashes.
An Egyptian tourist is in a critical condition after being hit by a police gas canister during anti-government protests in Istanbul.
A local hospital spokesman said 12 people suffered trauma injuries and hundreds suffered respiratory problems due to the effects of tear gas during the clashes around the city's Taksim Square.
The protest at Gezi Park started late on Monday after developers tore up trees.
However, it appears to have widened into a broader demonstration against Prime Minister Tayyip Erdogan's Justice and Development Party.
Riot police recently clashed with tens of thousands of May Day protesters in Istanbul.
There have also been protests against the government's stance on the conflict in neighbouring Syria, a recent tightening of restrictions on alcohol sales and warnings against public displays of affection.
Police staged a dawn raid on demonstrators who had been camping for days in Gezi Park in anger at plans to build a shopping mall, and clouds of tear gas rose around the area in Taksim Square that has long been a venue for political protest.
The Istanbul Medical Chamber, a doctors' association, said at least 100 people sustained minor injuries, some of them when a wall they were climbing collapsed as they tried to flee clouds of tear gas.
Amnesty International said it was concerned by what it described as "the use of excessive force" by the police against what had started out as a peaceful protest.
