ISTANBUL — Turkish Prime Minister Recep Tayyip Erdogan denounced protests against his government over the past three days as the work of extremists, while streets in central Istanbul remained barricaded, clashes flared again in Ankara, and financial markets plunged.

The premier was defiant at a press conference at Istanbul airport Monday before departing for a three-day trip to North Africa. He blamed the unrest on “extreme elements” working together with the main opposition party.

Erdogan said Turkey’s democracy means the protests can’t be compared with the Arab Spring, and that his party is restraining its own supporters from retaliating against demonstrators.

Istanbul was calmer Monday after a weekend of violent clashes between police and tens of thousands of demonstrators chanting anti-government slogans.

Sparked by protests against plans to redevelop a park near the central Taksim Square, the rallies broadened to target what demonstrators say is the Islamist-rooted Erdogan’s autocratic style, with grievances including alleged police brutality, curbs on alcohol sales, and restrictions on labor unions.

The protests spread throughout the country.

In Ankara Monday, police used tear gas and water cannon against a group of students, NTV television said. At least 1,500 people were detained in Ankara, Hurriyet Daily News reported, citing opposition lawmaker Aylin Nazliaka.

Stocks Slump

Turkey’s benchmark stock index slumped 7.9 percent at 3:30 p.m. in Istanbul, headed for its biggest drop in five years. Yields on two-year lira bonds jumped 36 basis points to 6.43 percent, and the lira fell 1 percent to 1.8938 per dollar.

Erdogan has presided over an economic boom and won three elections, each with an increased share of the vote, making him less vulnerable to the kind of unrest that swept away longtime leaders in Egypt and other Middle East countries two years ago.

He may, though, come under pressure to moderate a style of governing that has seen personal edicts, on issues ranging from the content of popular television shows to the role of parliament, transformed into proposals for new laws.

Erdogan is currently seeking support for a new constitution that would allow the president to issue decrees with force of law, dissolve parliament, call elections, and decide whether to use the army.

“Protests do not pose a threat to government stability, and are unlikely to threaten the ruling party’s re-election,” Naz Masraff, an analyst at Eurasia Group, which measures political risk, said in an email Sunday. “However, the protests will significantly constrain Erdogan’s ability to push for a presidential system in Turkey, as these events show he is increasingly perceived as becoming more authoritarian.”

Mosque Plan

On Sunday, Erdogan said the government would push ahead with the redevelopment of Taksim, including plans to build a mosque.

President Abdullah Gul sounded a more conciliatory note, calling for calm in a speech in Ankara Monday. He said that the protesters’ message had been received and called it a test for Turkey’s democracy, which he said isn’t just about elections.

Gul is a longtime ally of Erdogan, though local media have reported strains between them in recent years.

Turkey will hold its first public vote for the presidency next year when Gul’s term ends, and there’s speculation Erdogan may stand. Parliamentary elections are due the year after.

Erdogan has been seeking support for constitutional changes that would increase the powers of the office, currently largely symbolic. His party would need backing from at least one other group in the legislature to get the measures through. The main opposition parties are against the plan.

Gas Treatment

There were clashes over the weekend in 67 cities, Interior Minister Muammer Guler told reporters Sunday. One person was killed when a car drove into a crowd of protesters, while 1,740 people received treatment for injuries or effects of gas, Hurriyet said. Guler said 115 policemen were among the injured.

The protests began when police fired tear gas to clear demonstrators out of Gezi Park near Taksim, where they were resisting what they said were plans to cut down trees and build a new complex including a shopping center.

Activists used social media sites to organize gatherings, while local media mostly played down the events. Erdogan ordered an investigation into use of force by police.