Tensions are high in Turkey with the approach of the first anniversary of deadly nationwide anti-government protests and in the wake of an unprecedented mine disaster that claimed 301 lives last week.
"I have been informed that police were attacked by Molotov cocktails and a 30-year-old man was injured," Huseyin Avni Mutlu, the governor of commercial hub Istanbul, told reporters.
The governor added that a gun had been used in the incident but did not elaborate.
Dogan said police fired tear gas and water cannon at up to 20 protesters who denounced the death of a teenage boy who fell into a coma during anti-government unrest last year. They also protested last week's mine disaster in the eastern Turkish city of Soma.
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The news agency said the police also fired gunshots into the air, but an eyewitness who did not give his name told AFP that police fired live bullets at the crowd.
Demonstrators responded to the tear gas and water cannon by hurling stones and Molotov cocktails at police and setting fire to an armoured police vehicle, Dogan said.
Police also intervened twice when protesters attempted to march toward the hospital where the wounded man was being treated, an AFP photographer saw.
Around 400 demonstrators later staged a sit-in outside the hospital, chanting slogans: "Murderer state has taken another life."
Eight people, including the teenage boy and at least one policeman, died as a result of the anti-government unrest last year that erupted when police cracked down heavily on a peaceful campaign to save a small Istanbul park from redevelopment.