ISTANBUL, June 7 (Xinhua) -- Seven police officers and four civilians were killed and 36 others injured in the car bombing attack on a police shuttle bus in Istanbul on Tuesday, the governor said.

Three of the wounded "are in critical condition," Governor Vasip Sahin said on the scene.

He said the car bomb exploded at 8:40 a.m. local time (GMT 0540)  when the riot police shuttle bus passed by in the neighborhood of Vezneciler in Fatih district.

Many ambulances were dispatched to the scene, while police evacuated and cordoned off the area and halted the public transportation.

The deadly attack came one day after Turkey entered the holy month of Ramadan, a time when Muslims in the country practice fasting.

The security situation in Turkey has deteriorated in recent months, with Istanbul, the national capital of Ankara and other cities having been hit by a number of bombing attacks.

In Istanbul, two suicide bombing attacks killed 12 Germans and four foreigners respectively in January and March.