A protester in Istanbul died from a head injury and a police officer suffered a fatal heart attack during Turkey’s worst day of civil unrest since anti-government protests swept the nation last summer.

A protester in Istanbul died from a head injury and a police officer suffered a fatal heart attack during Turkey's worst day of civil unrest since anti-government protests swept the nation last summer, local media said late on Wednesday.

World Bulletin news website said that riot police clashed with demonstrators in several Turkish cities on Wednesday as mourners buried a teenager, wounded in the protests last June, whose death this week after nine months in a coma sparked a fresh wave of disturbances.

Police fired water cannon, tear gas and rubber pellets on a major Istanbul avenue to stop tens of thousands of protesters from reaching the central Taksim square.

There were similar scenes in the centre of the capital Ankara and in the Aegean coastal city of Izmir.

Officers in riot gear chased pockets of protesters into side streets late into the night.

The death on Tuesday of 15-year-old Berkin Elvan, who got caught up in street battles in Istanbul between police and protesters last June while going to buy bread for his family, has hit a raw nerve with many Turks.