In pictures: Police crack down on Turkish protests

Riot police have stormed an Istanbul protest square, firing volleys of tear gas at firework-hurling demonstrators after Turkish leader Recep Tayyip Erdogan warned he had "no more tolerance" for the mass demos against his Islamic-rooted government.

The unexpected police intervention in Istanbul's Taksim Square, which began early Tuesday morning, marked the first time officers returned to the area since pulling out more than a week ago. They fought hours-long battles with clusters of demonstrators, some of whom hurled back fireworks and Molotov cocktails.

Taksim Square turned into a battle scene as darkness fell, clouds of acrid smoke filling the site as police dispersed tens of thousands of protesters chanting "Erdogan, resign!" and "Resistance!", on the worst night of violence in 12 days of nationwide unrest. (Getty Images)

Riot police clash with protesters in Taksim square after two weeks of demonstrations in the city. (Getty Images)

A masked protester holds a box of fireworks during clashes against riot police. (AFP/Getty Images)

After riot police sent the large crowd scrambling with bursts of gas and jets of water, cat-and-mouse games with smaller groups of demonstrators continued into the night. (Getty Images)

A man walks past a burning vehicle amid anti-government protests in Turkey's capital. (Getty Images)

Tear gas is fired on a crowd gathered in Taksim square in Istanbul, after what began as a protest over the fate of Gezi Park turned into extended anti-government protests. (Getty Images)

A masked protester stands near a burning vehicle in Turkey's Taksim square. (Getty Images)

Riot police look on as protests continue. (Getty Images)

The assault on Taksim Square surprised protesters, many of whom were dozing in nearby Gezi Park, because it came after Prime Minister Erdogan said he would meet with protest leaders on Wednesday, his first major concession since the trouble began. (Getty Images)

Police brought in bulldozers to clear makeshift barriers in the early hours of the morning. (Getty Images)

(Getty Images)

The nationwide unrest first erupted after police cracked down heavily on May 31 on a campaign to save Gezi Park from redevelopment.

The trouble spiralled into mass displays of anger against Erdogan, who is seen as increasingly authoritarian, tarnishing Turkey's image as a model of Islamic democracy.

Erdogan said on Tuesday that four people, including a policeman, had died in the unrest. Nearly 5,000 demonstrators, many of whom are young and middle-class, have been injured.