A car bomb targetting a police bus in Istanbul killed 11 people, including seven officers, and wounded 36 others during the morning rush hour Tuesday.
Multiple ambulances were sent to the scene in the central historic district of Vezneciler, near Istanbul University and Bayezit Square, a popular tourist destination.
Witness Alaattin Didik- Male told VOA's Turkish service he had just parked his car in the area and was walking to breakfast when the blast occurred. He said he heard screams and ran in that direction, but stopped when he heard shooting. He then saw four policeman shouting that they were OK, but their colleagues were dead.
They had guns in their hands, shooting in air," he told VOA. "The police lost their minds. They were covered in blood."
After visiting the wounded being treated in Haseki hospital, Turkish President Recep Tayyip Erdogan said Turkey's fight against terrorists will continue to the end.
The blast, which occurred on the second day of the Muslim holy month of Ramadan, is the latest of several attacks in Istanbul and Ankara this year.
There has been no immediate claim of responsibility for the bombing.
French President Francois Hollande condemned the attack as "intolerable act of violence" that should strengthen common resolve to fight terrorism.
U.S. Ambassador to Ankara John Bass said in a Twitter message "such senseless violence could never be rationalized by any cause." The United States will "continue to stand shoulder-to-shoulder with Turkey in the fight against terrorism," Bass said.
NATO Secretary-General Jens Stoltenberg reaffirmed the alliance’s solidarity with Turkey against the global threat of terrorism.
“Terrorism seeks to undermine the very values” NATO stands for: “democracy, individual liberty, human rights and the rule of law,” Stoltenberg said, “It can never be tolerated or justified.”
EU foreign policy chief Federica Mogherini also reaffirmed support for Turkey.
Kurdish rebels fighting for autonomy in the country's southwest have been attacking police and military targets.
Last month, at least eight people, including soldiers, were wounded by a remotely-detonated car bomb targeting a military vehicle in Istanbul that was claimed by the Kurdish worker's party, or PKK.
Two blasts in Ankara claimed by the Kurdistan Freedom Falcons (TAK), a radical splinter group of PKK, claimed dozens of lives earlier this year.