Another 135,000 people could be badly injured and more than half a million could be left homeless, according to the scenario.

Istanbul, like many areas of Turkey, is close to a major fault line and has suffered major earthquakes in the past.

Some 18,000 people -- 1,000 of them in Istanbul -- were killed in a quake in northwest Turkey in August 1999 which had a magnitude of 7.4. Many of the deaths were blamed on sub-standard building.

Work on the report was conducted by four Japanese and 10 Turkish scientists and a team of engineers and was based on a night-time population of nine million people in the city.

The report assessed scenarios based on earthquakes with magnitudes of 6.9, 7.4, 7.5 and 7.7. It said 70,000-90,000 would be killed in the case of a quake of 7.5 or 7.7 magnitude.

The city council has prepared an earthquake master plan to cope with such a scenario, focused on assessing the strength of buildings and pulling them down or reinforcing them if necessary.

It did not give a forecast timescale for any possible earthquake. Experts have said previously there was 50 percent chance of a quake with a magnitude of at least seven hitting the city within three decades.

Istanbul has some 12 million inhabitants. (Reporting by Daren Butler; Editing by Caroline Drees)