A day after meeting with protest leaders and offering to hold a referendum on plans to redevelop Gezi Park, Erdogan resumed his combative stance on the environmental protest that has morphed into the biggest challenge to his Islamic-rooted government's decade-long rule.

"I'm making my last warning: mothers, fathers please withdraw your kids from there," Erdogan said in a live television broadcast on Thursday. "Gezi Park does not belong to occupying forces. It belongs to everybody."

Demonstrators have been camping out in the park since May 31, when police cracked down heavily on a small campaign to save the site's 600 trees from being razed.

The crackdown sparked an outpouring of anger across the country against Erdogan and his government, seen as increasingly authoritarian after more than a decade in power.

Erdogan inflamed tensions on Tuesday, when riot police stormed Istanbul's Taksim Square, the focal point of two weeks of protests, prompting a day of violent clashes with tens of thousands of protesters. The intervention fuelled fears that the adjoining Gezi Park would be cleared next.

"Don't sadden us anymore, let us clean Gezi park and return it to its rightful owners... the people of Istanbul," Erdogan said, urging environmental protesters to withdraw so that police could clear the site of "illegal organizations".

The ultimatum came after Erdogan on Wednesday made his first concession yet by offering to hold a popular vote on plans to build a replica of Ottoman-era military barracks in the park.

Demonstrators, many still reeling from Tuesday's violence that sent clouds of acrid tear gas into their tents, have reacted coolly to the referendum idea and criticized the government for cherry-picking the representatives invited to the talks.

"We don't agree (with the referendum). We are angry that Tayyip spoke to people who don't represent us," said 29-year-old Iskender Sisman, sitting outside a tent in Gezi Park.

"Tayyip must apologize for everything, for the park, for the tear gas," he added.

Erdogan, who has branded the protesters "extremists" and "looters", has faced international condemnation over his handling of the crisis.

Four people have been killed and nearly 5,000 demonstrators during the unrest, tarnishing Turkey's image as a model of democracy in the region.