Police have clashed with protesters in the Turkish capital Ankara and in Istanbul, on the second day of unrest initially sparked by plans to build a shopping centre on a city park.
Thousands of people packed into Istanbul's Taksim Square, near the Gezi Park, after police pulled out.
But the unrest then moved to the upmarket Besiktas district, where police fired tear gas and water cannon.
Officials said more than 90 protests had taken place across Turkey.
A total of 939 people had been arrested, the Interior Ministry said, as demonstrations took place in towns and cities including Antalya, Izmir and Konya.
Dozens of injures have been reported.
These are the largest anti-government protests in Turkey for years.
Prime Minister Recep Tayyip Erdogan said police had made "mistakes" in the force they have used, but has called for an end to the Istanbul protests.
He said Taksim Square "cannot be an area where extremists are running wild".
The protesters say Gezi Park in Istanbul is one of the few green spaces left in Istanbul, and that the government is ignoring their appeals for it be saved.
Their protest began with a small number of people staging a sit-in in the park at the start of the week.
On Friday, clashes broke out as police fired tear gas to try to clear them out.
Correspondents say that the protest has spiralled into widespread anti-government unrest and anger over the perceived "Islamisation" of Turkey.
The perception that police have been heavy-handed, a view adopted by many of the country's mainstream media, has also fuelled the unrest.
On Saturday, in a defiant speech to the exporters' union, Mr Erdogan said the plan to rebuild an Ottoman era military barracks on the Gezi Park site would go ahead as planned.
Referring to protesters fears that the site was destined to be a shopping centre, he said one "might be built on the ground floor or a city museum" but that this had not yet been decided.
But he also admitted there had been "some mistakes, extremism in police response", and that the authorities were investigating.
In an apparent bid to reduce tension, police and riot vehicles were withdrawn from the square on Saturday afternoon, and barricades removed, allowing thousands of people to enter the square and demonstrate.
One protester, Koray Caliskan, told the BBC people felt "victorious".
"This is the first time in Turkey's political history that a million people moved into Taksim Square to claim their public park," he said.
Another protester, Oral Goktas, told Reuters the protest had become one "against the government, against Erdogan taking decisions like a king".
The scene in the central square appeared to be peaceful, with protesters chanting slogans, dancing, waving banners and calling for the government to resign.
However the violent scenes then moved to the upmarket Besiktas area of the city, close to the Istanbul offices of the prime minister.
Police in Besiktas fired tear gas to hold back protesters, some of whom were throwing stones or cobbles.
The BBC's Shaimaa Khalil in Istanbul says the mood changed as darkness fell, and that the largely young crowd appeared to be growing increasingly agitated.
Similar clashes were seen on the streets of the capital, from where video footage emerged which appeared to show a group of protesters being run over by a water cannon vehicle.
Mr Erdogan has accused his opponents of using the anger over the Gezi Park issue to stoke up tensions.
The prime minister has been in power since 2002 and some in Turkey have complained that his government is becoming increasingly authoritarian.
His ruling AK Party has its roots in political Islam, but he says he is committed to Turkey's state secularism.
The US has expressed concern over Turkey's handling of the protests and Amnesty International condemned the police's tactics, saying: "The use of violence by police on this scale appears designed to deny the right to peaceful protest altogether and to discourage others from taking part."