From Nick Paton Walsh. Gul Tuysuz and Ben Brumfield

ISTANBUL (CNN) — Riot police fired massive clouds of tear gas across Taksim Square in Istanbul on Tuesday, sending protesters running.

Thick smoke blanketed the area — some of it wafting into Gezi Park, the central point of the protests.

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The government had promised to allow protesters to remain in Gezi Park, and it was not immediately clear whether authorities were firing into the park. But authorities appeared to be lining up close to the park.

As the tear gas fog began to lift, Taksim Square, the area in which tens of thousands of people had been gathered — and had been throwing rocks at riot police — was empty of protesters.

The assault — which also included authorities firing water cannons — came shortly after police, in heavy riot gear, withdrew from the park itself and moved to a nearby area.

It marked a return to the more heavy-handed tactics Turkish authorities used in the earlier days of the protests.

The protests at first had focused on the environment — opposition to a plan to build a mall at the park — but quickly grew into a battle against what demonstrators call the government’s increasingly authoritarian tactics.

Earlier Tuesday, police and protesters battled over a new barrier inside the square.

Protesters lobbed Molotov cocktails at armored vehicles and burned one. Police responded by spraying water cannons.

In a game of cat-and-mouse, the demonstrators, using wooden boards as shields, would pull back — only to return, lobbing cocktails and firecrackers and flashing “victory” signs.

“We will never allow people to push things to us, force things to us,” Prime Minister Recep Tayyip Erdogan told a gathering of his own Justice and Development Party in parliament. “And we will never force things either.”

After touting a long list of achievements in the country, which he credited to his government, Erdogan turned to the street demonstrators in Istanbul, who for more than a week have called for him to step down.

“They say the prime minister is harsh. The prime minister is firm,” Erdogan said of their grievances against him. “I’m sorry,” he answered them. “This prime minister is not going to change.”

Throughout Tuesday morning, smoke from tear gas and fireworks wafted through the air at Taksim Square as the armored vehicles shoved away makeshift barriers set up by the demonstrators.

Several protesters linked arms to form a human chain and prevent the police advance. But when police deployed multiple canisters of tear gas, they scattered again.

“If you stop throwing rocks, we will not use tear gas,” the police told the raucous group over loud speakers. “We don’t want you to get hurt; please obey.”

A show of force

The police movement came one day before Erdogan planned to meet with protest organizers. The presence appeared more to be a show of force at the square than an effort to flush out protesters who have been camped there for days.

The demonstrations in Turkey started as a small sit-in over plans to bulldoze Gezi Park — the last green space in central Istanbul — and replace it with a shopping mall.

But they have grown into a protest across the political spectrum.

Demonstrators have demanded Erdogan’s resignation, accusing his government of creeping authoritarianism.

The result has been the biggest challenge to Erdogan and his governing Justice and Development Party during their decade in power.

Erdogan fights back

And the prime minister has fought back.

In speeches, Erdogan has said he has no tolerance for what he calls illegal demonstrations.

Sunday, he slammed protesters, warning that “even patience has an end.”

He criticized protesters’ tactics and challenged them to beat him at the ballot box.

“All they do is destroy. They attacked public buildings; they burned public buildings. They burned the cars of civilians,” he said.

“Let’s face off at the ballot box in seven months. If you are saying democracy and freedom, if you are saying rights and freedoms, you cannot achieve that with violence. Only within the laws, you can achieve it.”

Violence at past protests

Previous protests have met with a harsher police response, garnering broad criticism from inside and outside of Turkey.

Since the demonstrations started on May 31, two protesters have been killed. One was hit by a car in Istanbul; the other was shot in the head by unknown assailants in Antakya, near the border with Syria.

A police captain died after falling from a bridge last week, the Adana governor’s office said.

The Turkish Medical Association said that more than 4,300 people were injured in clashes last week. Only a few dozen suffered serious injuries.

CNN’s Ivan Watson and Gul Tuysuz reported from Istanbul; Ben Brumfield wrote from Atlanta.

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