TURKISH riot police backed by water cannon have confronted around 1000 trade union workers in the capital Ankara, after a weekend of some of the worst clashes since anti-government protests erupted late last month.

Officers used megaphones to order workers to stop their march towards Ankara's central Kizilay district.

"Those of you on the streets must stop blocking the streets. Do not be provoked. The police will use force," they shouted, as several water cannon were positioned a few hundred metres away.

Further marches by striking workers were planned in Istanbul, despite government warnings that demonstrations would not be tolerated.

"There is an attempt to bring people to the streets through strikes and work stoppages. These will not be allowed," said Interior Minister Muammer Guler.

Prime Minister Tayyip Erdogan is seeking to restore calm after weekend unrest during which police fired tear gas and water cannon to clear thousands of protesters from around Taksim Square in Istanbul, the focal point of the demonstrations.

Police detained 441 people in connection with clashes in Istanbul on Sunday and 56 in Ankara. As violence across several cities entered its 18th day, at least four people have been killed and around 5000 injured, the Turkish Medical Association said.

What began as a small demonstration by environmentalists upset at government plans to build on a public park adjoining Taksim has grown into a movement against Mr Erdogan, who opponents say is overbearing and meddles too much in their personal lives.

"We are tired of protesting, we don't want to keep doing this, we want to return to our lives – but we are tired of this oppressive government constantly interfering," said Mahmet Cam, a teacher among the striking workers.

There were also clashes yesterday in the city of Eskisehir, around 125 miles south-east of Istanbul, where police used tear gas and water cannon to disperse crowds and cleared away hundreds of tents, reports claimed.

European Union Enlargement Commissioner Stefan Fuele expressed concern about developments in Turkey, whose negotiations to join the bloc have sputtered partly over worries about its record on human rights and freedom of speech. "Turkey needs de-escalation and dialogue, not continuation of excessive use of force against peaceful protesters. We watch with concerns," he tweeted.

Germany has long harboured doubts about admitting Turkey to the EU. Chancellor Angela Merkel said she was "appalled, like many others" and shocked at Turkey's tough response to the protests. "What's happening in Turkey at the moment is not in line with our idea of the freedom to demonstrate or freedom of speech."

Mr Erdogan sought to seize the initiative over the weekend by holding huge rallies in Istanbul and Ankara.

A defiant Mr Erdogan told supporters in Istanbul on Sunday the unrest had been manipulated by "terrorists" and dismissed suggestions he was behaving like a dictator.

A few miles away, police fought running battles with protesters in clashes that lasted well into the evening.