ANKARA, June 7 (Xinhua) -- The U.S. Embassy in Turkey on Tuesday warned its citizens to exercise caution during the Ramadan holiday over the deadly explosion in Istanbul.
"This morning, at approximately 8:45 a.m., there was a bomb explosion in the Vezneciler area of Fatih District in Istanbul... We strongly encourage U.S. citizens to avoid the area, maintain a high level of vigilance, monitor local media for updates, and exercise caution if you are in the vicinity," the statement said on its official website.
"No group has claimed responsibility for the attack, but extremist organizations or groups continue to issue non-specific warnings of terrorist attacks during the Ramadan holiday," the statement added.
Seven police officers and four civilians were killed and 36 others injured in the car bombing attack on a police shuttle bus in Istanbul earlier on Tuesday.
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.