Hundreds of thousands rallied in Istanbul today to show support for Turkey’s Prime Minister as he comes under increasing pressure from growing anti-government protests that have swept the country in the past two weeks.

The show of force by supporters of Recep Tayyip Erdogan came as police launched a violent crackdown on protesters opposed the government in another part of the city, using tear gas, water cannon and rubber bullets to disperse crowds.

The renewed unrest began overnight when police moved in forcibly to clear the camp at Gezi Park in Istanbul which has been the focus of anti-government protests. Within hours, large crowds took to the streets in support of the protesters, converging on the adjacent Taksim Square from all over the city.

But Mr Erdogan remained defiant. He flew into Istanbul today to give a speech before a crowd of his Justice and Development Party’s (AKP) supporters. “I did my duty as Prime Minister,” he said. We could not have allowed this and we will not allow it,” he said to roars of approval.

As he spoke, across town police were firing tear gas at anyone who set foot in the streets around Taksim. Armoured vehicles moved through the streets, protesters had piled up barricades of rubble and twisted metal; and everywhere there was the smell of tear gas.

Only 24 hours before, many believed the worst of the unrest was over. A compromise appeared to have been reached: Mr Erdogan had agreed to hold off the bulldozers from Gezi Park, where plans to build a shopping mall had sparked the protests.

Then Mr Erdogan made the first of his defiant speeches, at a party rally outside Ankara. “Nobody can intimidate us. We don’t take orders from anybody except God,” he said, and ordered the police in to clear the camp by force. As they moved in with rubber bullets and tear gas word spread and people came out on to the streets.

Police fired tear gas on crowds of peaceful protesters at close range: a child was knocked unconscious by the gas being carried away. Police turned water cannon on to the German Hospital, where wounded protesters had retreated, and there were reports they stormed the emergency department. They also stormed hotels where protesters had taken shelter, tear-gassing the lobby of one where German MPs were staying. But the protesters refused to be cowed, and crowds moved through the city chanting against Mr Erdogan throughout the night.

Day did not bring calm. The streets of Istanbul rang to the protesters’ chants, and tear gas was fired without warning. Many of those out on the streets were not protesters but ordinary residents trying to stock up on food. Some had small children with them. Police fired on them as well.

Vigilantes or plain clothes officers working alongside the police then charged the panicking crowds with clubs. So much tear gas was fired around the city that it invaded the apartments of those who had nothing to do with the protests.

There were many arrests and reports that lawyers were being denied access to those detained. Those reported arrested included doctors who were detained for treating the injured, and four Turkish journalists. There were photographs on Twitter today showing what appeared to be doctors in white coats with their hands bound in plastic handcuffs.

The government flew thousands of riot police reinforcements into Istanbul, including from the south-east, where security forces are notorious for their violence during the war against Kurdish separatists.

Meanwhile Mr Erdogan seems determined to hold the spectre of religious strife over the heads of the protesters, repeatedly calling on his supporters’ Muslim sensitivities. He accused the protesters of defiling mosques and beating women in headscarves – though there is no evidence they did either.

Police earlier dispersed a memorial service in the capital for a protester who died of injuries during a demonstration. There was also unrest today in Ankara, where police fired tear gas and water cannon to clear demonstrators in Kizilay Square. At least four people were injured.

Witness: war zone

Ilhan Tanir @WashingtonPoint

“1 hour after PM Erdogan’s ultimatum of 24 hours, police currently attacking and evacuating Gezi Park protesters” 7:54pm – 15 June

Sebnem Arsu @sebnemarsu

“Panic, chaos, tension, violent here at Divan hotel, people been circled by police, tear gas smoke intense, windows almost smashed” 10:03pm – 15 June

Önder Vincent Koç @koconder

“Bulldozers in Taksim Sq, medical tent has been tear gas. Press has been held back and phone lines killed” 8:38pm – 15 June

Chapulcu Asli @sofia_blk20h

“Police attacked again 2 Taksim Square while there were lots of kids in the crowd, Gezi Park emptied” 8:42pm – 15 June

Ceylan Yeginsu @CeylanWrites

“Water cannons and tear gas being fired in #Ankara’s Kizilay Square where people are gathering for the memorial service of Etem Sarisuluk...” 12:39pm – 16 June

Bel Trew @BelTrew

“Police surrounding #taksim – sporadically not letting people in. 100s of security forces all over #gezipark”. 1:18pm – 16 June

Benjamin Harvey

“4 journalists detained as clashes continue on the far end of Istiklal Street from Taksim Square” 4:12pm – 16 June

MahirZeynalov @MahirZeynalov_

“Crowd is wild, Erdogan is very angry. The atmosphere is incredible” 5.19pm – 16 June