Mehmet Ayvalitas, a 20-year-old member of a computer hacking group, was hit by a taxi late Sunday as he and other protesters organized a demonstration in Istanbul's Umraniye district, said the Turkish Doctors' Union and Turkish press reports.
The doctors' group also reported that more than 2,300 people have been injured during the protests, a much higher casualty count than the government has provided.
The union said the vehicle that struck the protester failed to stop despite warnings and drove into the assembled demonstrators. It alleged that the driver was incited by incendiary remarks made by Prime Minister
Erdogan's policies have been a target of the demonstrations, which began as a reaction to government plans to bulldoze Taksim Gezi Park, one of central Istanbul's last major green areas, and replace it with a shopping mall and a replica of an Ottoman-era barracks.
Protesters have accused Erdogan, who has been in power for a decade, of taking Turkey down the road of authoritarian and Islamist rule. Erdogan, who has triumphed with wide electoral majorities, has dismissed the protesters as militants and losers.
The doctors' group estimates 1,480 people have been injured in the clashes in Istanbul, with five remaining in intensive care. An additional 834 people were treated in Ankara and coastal Izmir, local media reported.
The figures are significantly higher than those offered Sunday by Turkey's interior minister, Muammer Guler. He said 173 people were injured in the violence. Of those, the government said, 115 were police officers and 58 were protesters.
Police have been using batons, tear gas and water cannons to put down the spreading protests, which entered a fourth day Monday. The unrest is regarded as the broadest protests in decades to hit Turkey.