Bellowing to the din of drums and wailing Turkish pipes, teachers, doctors, bank staff and others marched in a sea of red and yellow union flags in the capital Ankara and in Istanbul, where they converged peacefully on Taksim Square, the epicentre of nearly a week of violent clashes.
"Taksim, resist, the workers are coming!" they chanted in Istanbul, directing most of their anger at Erdogan, who has dismissed the protesters as "extremists" as he grapples with the biggest challenge to his decade in power.
The striking workers had earlier unfurled banners addressing Erdogan, reading: "This nation will not bow to you!" and "Taksim Square is everywhere!"
Two people have been killed in the six days of unrest nationwide, according to doctors and officials. The national doctors' union said more than 4,000 had been injured, 43 of them severely, in protests police have sought to quell with tear gas, pepper spray and water cannon.
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Turkey's Western allies have voiced concern in recent days about reports of police violence but Ankara has hit back at criticism of its handling of the crisis, a foreign ministry source told AFP.
Asked if that was Washington's view of its key NATO ally, State Department official Jen Psaki told reporters: "No."
But she insisted "we have had concerns over the past couple of days about instances of police brutality," Psaki said.
Davutoglu assured Kerry an investigation was under way into the police response and played down the demonstrations, likening them to the Occupy Wall Street movement in the US in 2011, the source said.
"Erdogan needs to apologise, resign and go to court for the things he has done, for the excessive force," said Tansu Tahincioglu, a 26-year-old web entrepreneur in Istanbul.
"Before, people were afraid to express their fear publicly. Even tweets are a problem. But now they are not afraid," he told AFP.