ISTANBUL, June 16 (Xinhua) -- Turkish Prime Minister Recep Tayyip Erdogan on Sunday warned of stern punishment for people responsible for the ongoing unrest in his country.

"Those who terrorized for 18 days will pay the price within the boundaries of law," he said when addressing hundreds of thousands of people at Kazlicesme square in Istanbul.

"We will trace the social media to find those who have provoked incidents," he said.

"Now, Gezi Park has been cleared and handed back to its people. The municipality has cleared the park and renewed it with new flowers," said the prime minister.

Tight security measures have been taken ahead of the Sunday pro- government rally. All the roads leading to the Kazlicesme square were closed and the police surrounded the whole area with barriers.

About 1,000 riot policemen were brought to Istanbul from the southeastern and eastern provinces to support their colleagues.

Over two weeks ago, the protests in Turkey erupted when a group of activists gathered in Gezi Park to oppose the government plan to build a replica of Ottoman-era barracks in its place as part of a renewal project for the adjacent Taksim Square.

Hundreds of people joined the group after police used pepper spray and tear gas to disperse the protesters. Shortly after, thousands of people took to the streets in Istanbul and across the country to support the demonstrators and protest the policies of Erdogan's government.

Clashes between the police and protesters across Turkey have killed at least five people, including a policeman, and injured some 5,000.