At least eight people, including seven police officers, have been hurt in a gunfight during a raid against an armed group in Istanbul, the city's governor has said.
The shooting broke out soon after police began their raid on an apartment block in the Bostanci area of the city at 5.30am (02:30GMT) on Monday.
"These are extreme leftist, separatist and radical groups. There are more than 10 [people] detained in the operations," Muammer Guler, the governor of Istanbul, told the broadcaster NTV.
"Terrorists responded by throwing bombs in some places and seven policemen were wounded," Guler said. He did not specify which group had been targeted.
An onlooker was also shot in the head with a stray bullet, a photographer from the Associated Press reported.
The man showed no signs of life, television footage showed. It is unclear whether the man died from his injuries.
Automatic gunfire and sporadic blasts were heard as the raid went ahead, and tear gas was used by the police, witnesses said.
The police had raided more than 60 areas overnight in an attempt to crack down on armed groups alleged to be planning attacks on public targets.
"They were planning to stage sensational armed attacks soon," Guler said.
"We have seized lots of weapons, bombs and booby traps."
Turkey has in recent years focused its efforts on tackling members of the Kurdistan Workers' party (PKK), a group fighting for greater autonomy for the Kurdish community.
But several armed left-wing and radical religious groups are also active across the country.
The police raids came days before May Day, when the authorities are usually put on alert for possible clashes with opposition groups.