Turkish police have used tear gas and water cannon against protesters occupying a park in central Istanbul.
Scores of people have suffered injuries, several of them when a wall collapsed during a police chase, the BBC reports.
Demonstrators had been camping since Monday in Gezi Park, angry at plans to develop it as part of a revamp of Taksim Square, in which it is situated.
Many protesters also expressed discontent with the government of Prime Minister Recep Tayyip Erdogan.
Mr Erdogan has been in power since 2002 and some in Turkey feel that his government is becoming increasingly authoritarian.