Heavily-armed police special forces surrounded the apartment block, on the Asian side of Turkey's largest city, where police launched their raid in early morning.
İstanbul Governor Muammer Güler told broadcasters that the police raid was one of more than 60 carried out in İstanbul overnight against Islamist and lefitst militants suspected of planning "sensational attacks".
State-news agency Anatolian said police detained a total of 50 people in raids in seven cities across Turkey.
Thick smoke billowed from the apartment block in Istanbul where residents were believed to be trapped inside their homes after police launched their raid at 5.30 a.m. (0230 GMT).
Television images showed a man lying motionless on the ground near the apartment block and media said he was a television cameraman who had been shot by the militants. Another civilian was also shot by the militants, who are believed to be armed with explosives.
Occasional gunshots rang out as the stand-off continued several hours later. Police sought to keep locals away from the apartment block while ambulances were stationed at the ready.
Islamist radicals have carried out bomb attacks in predominantly Muslim Turkey in the past, most notably in 2003 when al Qaeda militants killed more than 60 people in a series of bombings in İstanbul.
"These are extreme leftist, separatist and radical groups. There are more than 10 detained in the operations. Terrorists responded by throwing bombs in some places and seven policemen were wounded," Güler said.
Turkey has also cracked down on members of the terrorist Kurdistan Workers Party (PKK). Several armed leftist, as well as radical Islamist groups, are active in Turkey.
Photos:
Benzer Haberler 
National
