Turkish police have arrested several people holding a silent protest in Istanbul's Taksim Square.
Turkey has seen violent anti-government protests in several cities across the country for nearly three weeks.
The government said Monday it may use the army to help stop the protests, if police power is not enough.
Two major Turkish trade unions held a nationwide strike Monday against the police crackdown on Gezi Park demonstrators. The unions, which together represent hundreds of thousands of workers, called for police violence to "end immediately."
Most of the strikes were peaceful, but riot police faced off briefly Monday with about 1,000 trade union workers in the capital, Ankara. More marches took place in other cities, despite government warnings they would not be tolerated.
Small-scale clashes with protesters occurred in Istanbul on the sidelines of a demonstration called by labor groups.
On Sunday, Turkish Prime Minister Recep Tayyip Erdogan told hundreds of thousands of supporters it was his "duty" to evict the activists from Gezi Park and the adjacent Taksim Square. He said the street protests were manipulated by "terrorists." He dismissed opposition allegations that he was behaving like a dictator.
Protests that started nearly three weeks ago against government plans to tear down the park for new construction quickly built into nationwide protests against Mr. Erdogan. The demonstrators accuse him of imposing his conservative Islamic views on the country.
The prime minister told protesters last week that he would put redevelopment plans for the park on hold until a court rules on them. He also said he would hold a referendum on the issue if the court rules in the government's favor.