The governor of Istanbul vowed tonight to continue efforts day and night to rid Taksim Square of anti-government protesters after an eleventh day of clashes.
It was in this square, and the adjoining Gezi Park, that a nation-wide movement was sparked after what was widely seen as a heavy-handed police response to a small protest against a construction project.
There was no apparent change in tactics today as police repeatedly used volleys of tear gas and water cannon to clear the square.
Protesters fought back with rocks, fireworks and petrol bombs, stubbornly returning to the square each time the ranks of riot police withdrew.
ITV News' Special Correspondent Rageh Omaar reports:
Turkey's President Recep Tayyip Erdogan had earlier warned protesters to stay away from the ramshackle camp of tents and barricades built up over more than a week of occupation.
"They say the prime minister is rough," he declared. "So what was going to happen here? Were we going to kneel down in front of these [people]?
"If you call this roughness, I'm sorry, but this Tayyip Erdogan won't change," he told a meeting of his AK party's parliamentary group.
After the area was cleared for the first of many times, bulldozers and water cannon moved in to level the barricades and extinguish the burning wrecks of vehicles.
But no sooner had police withdrawn than protesters flooded back onto the square to begin chanting and setting new fires.
At one stage, the volleys of tears gas were landing so quickly that a shroud of white mist hung over the entire area.
Photographs taken in the Beyoglu district of the city, almost a kilometre (0.6 miles) from where the clashes were taking place, showed residents wearing gas masks as they went about their lives.
Twitter users claiming to be in Taksim Square reported "extreme violence" and that many people were "injured" and "desperately hurt".
Footage from the square showed some apparently unconscious protesters being carried to waiting ambulances.
One video appeared to show a protester in a wheelchair being targeted by a water cannon.
The protesters accuse Mr Erdogan of overreaching his authority after 10 years in power and three election victories.
Some are also concerned at his promotion of what some see as Islamic policies despite the country's secular constitution. Recent legislation restricting the sale and advertisement of alcoholic drinks has been particularly controversial.
Mr Erdogan has promised to meet some of the members of the original demonstration in Gezi Park on Wednesday.