For more than two weeks, protesters had flouted Erdogan's warnings to vacate the area around the city's Taksim Square.
Yesterday evening, he ran out of patience. As dusk fell, hundreds of white-helmeted riot police swept through Taksim Square and Gezi Park, firing canisters of the acrid, stinging gas as they stormed through the tents set up throughout the park.
The protests began as an environmental sit-in to prevent a development project at Gezi Park, but have quickly spread to dozens of cities and spiralled into a broader expression of discontent about what many say is Erdogan's increasingly authoritarian decision-making.
He vehemently denies the charge, pointing to his strong support base which allowed him to win his third consecutive term with 50 per cent of the vote in 2011.
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As police cleared the square, many ran into nearby hotels for shelter. A stand-off developed at one hotel on the edge of the park, where police opened up with water cannons against protesters and journalists outside before throwing tear gas at the entrance, filling the lobby with white smoke. At other hotels, plain-clothes policemen turned up outside, demanding the protesters come out.
As news of the raid broke, thousands of people from other parts of Istanbul gathered and were attempting to reach Taksim. Television showed footage of riot police firing tear gas on a highway and bridge across the Bosphorus to prevent protesters from heading to the area.
Demonstrations also erupted in other cities. In Ankara, at least 3,000 people swarmed into John F Kennedy street, where opposition party legislators sat down at the front of the crowd facing the riot police not far from Parliament. In Izmir, thousands converged at a seafront square.