Turkish Prime Minister Recep Tayyip Erdogan on Sunday told a crowd of more than 100,000 supporters it was his "duty" to order a crackdown on an Istanbul protest park, as police and anti-government demonstrators faced off in fresh clashes.

A full day after riot police dislodged thousands of protesters occupying Gezi Park, officers in the city were still firing tear gas and jets of water at pockets of protesters determined to regroup.

Some 10 kilometres (six miles) away, in a much bigger park, Erdogan put on a show of strength for supporters of his ruling Justice and Development Party (AKP), drawing the largest crowd yet since the demos against his government erupted more than two weeks ago.

Addressing the cheering sea of people, many of whom wore white AKP caps, a combative Erdogan said protesters had forced his hand by defying repeated warnings to clear out of the park.

"I said we were at an end. That it was unbearable. Yesterday the operation was carried out and it was cleaned up," Erdogan said. "It was my duty as prime minister."

The violence sparked by the Gezi Park evacuation marked a major escalation in mass unrest that has posed the biggest challenge yet to the Islamic-rooted government's decade-long rule.

Two of Turkey's main trade union federations, KESK and DISK, announced they would go on strike Monday in protest at the latest police clashes.

Turkey's political turmoil first began when a peaceful sit-in to save Gezi Park's 600 trees from being razed prompted a brutal police response on May 31, spiralling into countrywide demonstrations against Erdogan.

The crisis has claimed four lives and injured nearly 7,500 people so far, according to the Turkish Medical Association.

Saturday evening's intervention in Gezi Park saw officers with gas masks and riot shields storm the patch of green, sending thousands of campers scrambling out of their tents to escape clouds of acrid tear gas.

Many sought refuge in the luxury hotels bordering the park, prompting police to douse the lobby of at least one five-star establishment with water as guests choked on tear gas fumes.

Thousands of demonstrators took to the streets in the capital Ankara and the western city of Izmir in solidarity overnight.

Throughout Sunday, clusters of protesters in Istanbul engaged in hours-long cat-and-mouse games with police. The demonstrators, in dispersed groups that numbered in the hundreds, chanted "Erdogan, resign!" and at times hurled back stones and plastic bottles.

Many complained that the water cannons were spraying water mixed with pepper spray, leaving protesters and passers-by alike coughing in the streets.

Ankara also saw fresh police clashes. As evening fell, some people leaned out of their windows banging pots and pans to support the demonstrators.

Opponents accuse Erdogan of authoritarian tendencies and of forcing Islamic conservative reforms on the mainly Muslim but staunchly secular nation of 76 million.

But the 59-year-old, who has been in power since 2002, remains hugely popular. The AKP has won three elections in a row and took nearly half the vote in 2011, having presided over strong economic growth.

-- 'Gezi Park returned to the people' --

The Taksim Solidarity group, seen as most representative of the protesters, said "hundreds" had been injured in the weekend unrest, while Istanbul governor Huseyin Avni Mutlu put the number at 44.

Amnesty International said it believed dozens had been detained.

Gezi Park and the adjoining Taksim Square, another focal point for the protests, were sealed off Sunday and heavily guarded by police.

Yellow tape lined the area, blocking entry to pedestrians, as bulldozers broke up protesters' makeshift barricades and municipal cleaners returfed grassy areas and planted fresh flowers.

"Gezi Park and Taksim Square have been evacuated and returned to the people," Erdogan told the party faithful.

Erdogan has taken a tough line on the protesters but made an unexpectedly conciliatory gesture when he held talks with Taksim Solidarity representatives on Friday.

He offered to suspend the Gezi project pending a court ruling on its legality, if protesters agreed to leave.

But the group rejected the olive branch, saying the government had failed to address all their demands, which include a call for arrested demonstrators to be released and for police chiefs in cities that saw clashes to be sacked.

The United States and other Western allies, along with human rights groups, have widely criticised Erdogan's handling of the crisis.

Germany on Sunday again urged Turkey to respect the right to demonstrate.

"Freedom to demonstrate and freedom of expression must be guaranteed and peaceful citizens respected," government spokesman Steffen Seibert said in a tweet.