Turkish Prime Minister Tayyip Erdogan has accused anti-government protesters of walking "arm-in-arm with terrorism" after three days of some of the most violent riots in decades.

Hundreds of police and protesters have been injured since Friday, when a demonstration to halt construction in a park in an Istanbul square grew into mass protests against what opponents call Mr Erdogan's authoritarianism.

Protests have been held in dozens of cities.

The demonstrations showed no sign of abating today with protesters gathering again in Taksim Square.

Barricades of rubble hindered traffic alongside the Bosphorus waterway and blocked entry into the area.

Leftist groups hung out red and black flags and banners calling on Mr Erdogan to resign and declaring: "Whatever happens, there is no going back."

In Ankara, protesters threw up a barricade in the Kizilay government quarter and lit a fire in the road as a helicopter circled overhead. Police charged demonstrators, mostly teenagers, and scattered them using tear gas and water cannon.

Mr Erdogan has dismissed the protests as the work of secularist enemies never reconciled to the mandate of his AK party, which has roots in Islamist parties banned in the past but which also embraces centre-right and nationalist elements.

The party has won three straight elections and overseen an economic boom, increasing Turkey's influence in the region.

"This is a protest organised by extremist elements," Mr Erdogan said at a news conference before departing on a trip to North Africa. "We will not give away anything to those who live arm-in-arm with terrorism."

"Many things have happened in this country, they've hanged, they've poisoned, but we will walk towards the future with determination and through holding onto our values," he added, an allusion to Turkey's murky past of military coups.

Turkey's leftist Public Workers Unions Confederation (KESK), which represents 240,000 members, said it would hold a "warning strike" on 4-5 June to protest over the crackdown on what had begun as peaceful protests.

The unrest delivered a blow to Turkish financial markets that have thrived under Mr Erdogan. Shares fell more than 10% and the lira dropped to 16-month lows.

Since taking office in 2002, Erdogan has dramatically cut back the power of the army, which ousted four governments in the second half of the 20th century and which hanged and jailed many, including a prime minister.