Protesters and Turkey’s prime minister both refused to back down Tuesday in what could become the final battle for Istanbul’s Taksim Square, the symbol of nationwide grievances against his government.

Tens of thousands of protesters returned to the square in the evening, in a show of defiance met with tear gas, rubber bullets and water cannons, hours after riot police had forced their way past improvised barricades to clear the square of protesters occupying the area for the past 12 days.

Hundreds more vowed to continue their sit-in at Taksim’s adjacent Gezi Park, despite an order from Prime Minister Recep Tayyip Erdogan for them to leave — an order bolstered by the police show of force.

A peaceful demonstration against the park’s redevelopment that began more than two weeks ago has morphed into the biggest test of Erdogan’s authority in his decade of power.

The unrest has spread to 78 cities across the country, with protesters championing their objections to what they say is the prime minister’s increasingly authoritarian style and his perceived attempts to impose a religious and conservative lifestyle in a country with secular laws — charges he rejects.

So far four people have died, including a policeman, and about 5,000 have been treated for injuries or the effects of tear gas, according to the Turkish Human Rights Foundation.

Tuesday’s clashes, which saw police and protesters take and lose control of the square several times, came a day after Taksim saw its smallest gathering since the demonstrations began, sparked by a violent police reaction against a sit-in in the park to prevent its redevelopment. The government had also said Erdogan would meet with some of those occupying the park today to hear their views.

“The relative calm yesterday was deceptive,” said Robert O’Daly, Turkey analyst for the Economist Intelligence Unit.

“Mr. Erdogan’s offer of dialogue appears to have been merely tactical. The appearance of riot police in the square this morning and renewed use of tear gas against the protesters fits better with his defiant rhetoric,” said O’Daly.

Erdogan, a devout Muslim, says he is committed to Turkey’s secular laws and denies charges of autocracy. Yet as he defended his tough stance, he gave critics little hope of a shift in his position.

“To those who … are at Taksim and elsewhere taking part in the demonstrations with sincere feelings: I call on you to leave those places and to end these incidents and I send you my love. But for those who want to continue with the incidents I say: ‘It’s over.’ As of now we have no tolerance for them.”

“Not only will we end the actions, we will be at the necks of the provocateurs and terrorists, and no one will get away with it,” he added.

His words, accompanied by the repeated rounds of tear gas that left many choking for breath, seemed to gird the resolve of many in the park rather than weaken it.

“People are definitely going to stay. The more the police attack, the more people come and stay,” said Melda, a 29-year-old cook who rushed to the park Tuesday morning when she heard of the police intervention. Fearful of losing her job for participating in the protests, she asked that her surname not be used.