Waving Turkish flags, demonstrators shout slogans against Prime Minister Recep Tayyip Erdogan during a June 6 protest on Taksim Square in Istanbul. (Aris Messinis/AFP/Getty Images)

Striking a defiant tone after a week of demonstrations that have roiled Turkey, Prime Minister Recep Tayyip Erdogan said Thursday that he would not abandon plans to raze a park in central Istanbul despite protesters’ objections.

At a news conference in Tunisia — the birthplace of the Arab Spring revolutions — the Turkish leader blamed terrorists for spreading the protests that have swept to dozens of cities, although he acknowledged that some of the tens of thousands who have turned out were motivated by environmental concerns.

The hotly anticipated remarks — Erdogan’s first about his domestic troubles since he left Monday on a goodwill tour of North Africa — did little to satisfy the thousands of people who have taken over Istanbul’s central Taksim Square, many of whom appear to be digging in for an extended fight.

“A state cannot be managed with a mentality of bargaining,” Erdogan said, saying he would give no ground in his plans to raze Gezi Park, the last large green space in central Istanbul, in favor of a replica of an Ottoman-era military barracks that once stood on the site. Demonstrations at the site mushroomed after police used tear gas and water cannons against a peaceful and initially small group of protesters last week.

“We said we are sorry for the tear gas used, but there is no country in the world that does not use tear gas,” Erdogan said.

He said that Turkey had evidence that the same left-wing Marxist group it blamed for a February attack on the U.S. Embassy in Ankara was involved in the protests this week.

“They have been caught on the streets and in social media,” he said. “What we are doing now is just protecting the rights of the majority.”

As Erdogan spoke at the joint conference with his Tunisian counterpart, Turkey’s main stock exchange dropped as much as 8 percent, a sign of the degree to which investors have been rattled by the recent unrest. Even many protesters credit Erdogan with rejuvenating Turkey’s economy, but analysts said that the longer the protests drag on, the larger their financial impact. Many streets around Istanbul’s center are shut to traffic by barricades built by protesters.

Protesters who took to the streets last Friday were initially motivated by environmental concerns related to the park’s demolition. But they quickly shifted to broader complaints about what many say is a steady erosion of secular freedoms. Erdogan announced plans last month to push for new restrictions on alcohol consumption, a symbol, some here say, of his desire to impose an Islamic vision of the country on what had long been a strictly secular state. Others complain about his advice to newlyweds to have at least three children — again seen as an inappropriate religious-tinged push into the private lives of Turkish citizens.

Many protesters in the sycamore-filled park, which has been filled with tents and venders selling kebabs and grilled fish, said that they felt that Erdogan’s policies failed to take into account the half of the country that did not vote for his socially conservative Justice and Development Party.

Erdogan “is the legitimate representative of half of Turkey,” said Nuray Mert, a columnist at Istanbul’s Hurriyet Daily. “He doesn’t get it.”

Though most of the protesters in Istanbul appeared to come from Turkey’s largely secular, educated middle class, one former Erdogan supporter said Thursday that he had been alienated by the violent reaction to the protests.

“Before these protests, I loved Erdogan. I voted for him three times,” said Murat Avcioglu, 28, an arcade owner in the working-class Kasimpasa neighborhood of Istanbul where Erdogan grew up and that is still a bastion of his support.

“He developed this country,” Avcioglu said, pointing to an economy that is the envy of many of its European counterparts. “But at some point, he started to say, ‘I’ll do whatever I want.’ ”

“I don’t understand why the police are behaving in this way,” Avcioglu said.

Also Thursday, Interior Minister Muammer Guler said that police had detained 117 people connected to the protests, seven of them foreign citizens, including one American. Most of them had been released. Turkish officials said that a police officer was killed Thursday after falling from an overpass while trying to restrain protesters. Two protesters had already been reported killed.