ISTANBUL — Violent protests against the government of Prime Minister Recep Tayyip Erdogan engulfed this city on Saturday, as thousands of demonstrators took to the streets and alleyways in a second day of civil unrest and faced the tear gas and water cannons of a harsh police crackdown.

Mr. Erdogan, in a televised speech Saturday morning, vowed to go forward with a plan to remake a city park in Taksim Square into a replica Ottoman-era army barracks and mall, the move that set off the initial protests earlier in the week.
For many demonstrators, however, the protest has moved beyond that project and become a broad rebuke to the 10-year leadership of Mr. Erdogan and his Islamist-rooted Justice and Development Party, which the protesters say has adopted authoritarian tactics.
Mr. Erdogan, in his first comments on the growing unrest, seemed determined to maintain the aggressive police response to the demonstrations. His only conciliatory note was to promise to investigate claims of excessive police force against peaceful protesters on Friday that resulted in nearly 1,000 injuries, according to the Turkish Doctors Association.
“The police were here yesterday, they will be there today, and they will be there tomorrow in Taksim,” Mr. Erdogan said.
By late afternoon, the police were pulling back from Taksim Square, allowing tens of thousands of protesters to enter and to continue the protest unhindered.
The widening chaos here and the images it produces threaten to tarnish Turkey’s image, which Mr. Erdogan has carefully cultivated, as a regional power broker with the ability to shape the outcome of the Arab Spring revolutions by presenting itself as a model for the melding of Islam and democracy.
Now Turkey is facing its own civil unrest, and the protesters have presented a long list of grievances against Mr. Erdogan and his government, including opposition to its policies of supporting Syria’s rebels against the government of President Bashar al-Assad, its crackdown on dissent and its intimidation of the news media.
“He criticized Assad, but he’s the same,” said Murat Uludag, 32, who stood off to the side as protesters battled with police officers down an alleyway near the Pera Museum. “He’s crazy. No one knows what he’s doing or thinking. He’s completely crazy. Whatever he says today, he will say something different tomorrow.”
Many of the protesters, some of whom voted for Mr. Erdogan, said they had grown tired of his leadership, which they said had become increasingly dictatorial. Mr. Erdogan still maintains a strong power base among religious conservatives, who represent a large voting bloc.
“When he first came to power he was a good persuader and a good speaker,” said Serder Cilik, 32, who was sitting at a tea shop watching the chaos unfold. Mr. Cilik said he had voted for Mr. Erdogan in the past but would never do so again.
An older man standing nearby, overhearing the conversation, yelled, “Dictator!”
Mr. Cilik, who is unemployed, continued: “He brainwashed people with religion, and that’s how he got the votes. He fooled us. He’s a liar and a dictator.”
Protests that began days earlier as a peaceful sit-in against the demolition of a central park have widened to neighborhoods across Istanbul and to other cities around the country, including Ankara, the capital. The protests turned violent on Saturday as police forces tried to disperse people with tear gas and some protesters pelted them with rocks, calling them “murderers” and “fascists.”
Police helicopters flew low over Istiklal Street, a main pedestrian thoroughfare, which would normally be clogged with tourists but on Saturday resembled a war zone, with shops shuttered and antigovernment graffiti sprayed on some shop windows. Using the Turkish initials of Mr. Erdogan’s party, one message on the facade of a department store, in blue spray paint, read, “A.K.P. to the grave, the people to reign.”
As they winced and rubbed their eyes of tear gas, protesters wagged their middle fingers at the helicopters and chanted that the government should step down.
On streets running off Istiklal, young men tore up granite slabs from the sidewalk and bashed them against the road, picking up the splintered pieces to throw at the police. On some streets protesters set up makeshift barricades with trash cans, panels of wallboard from construction sites and potted plants taken from outside fancy hotels.
On another major boulevard, protesters stopped a municipal water truck, which they believed was on its way to refill the police water cannons, and opened its valves, flooding the street. Nearby, protesters marched past the headquarters of the state television network, T.R.T., shouting, “Burn the state media!”
Many of the protesters complained about the lack of coverage on Turkish television, and said the silence of much of the local news media would help the protest movement grow because people, unable to see events on television would want to see them for themselves. Some newspapers also were largely silent on the protests: on Saturday morning the lead story in Sabah, a major pro-government newspaper, was about Mr. Erdogan promoting a campaign against smoking.
His party has accused opposition parties of stoking the protests, and in the late afternoon, Mr. Erdogan weighed in on Twitter: “Their issue is, how can we hit the A.K.P.? Wherever they try to hit us, we will stand tall and strong.”