The bomb appeared to have exploded inside the security checkpoint at the entrance of the embassy.
Private NTV television said two security guards at the entrance were killed.
A number of groups ranging from Kurdish separatists to leftist and Islamist militants have launched attacks on western nations in recent years in Turkey, which is a member of Nato.
The attack could also be linked to Syrian conflict as recently the Nato had deployed Patriot missiles on the border to defend Turkey against Syrian warplanes.
Over the years US embassies have been targets of protests and violence by terrorist groups and fringe elements trying to make a point.
Dar es Salaam, Tanzania, and Nairobi, Kenya, Aug 7, 1998: One of the horrific attacks that had a tag of Osama Bin Laden. The bombings resulted in 223 deaths and over 4,000 people maimed. The bombings are believed to have been in retaliation for the arrest and torture of four members of the Al-Qaeda affiliate.
Beirut, Lebanon, April 18, 1983: A suicide car bomb killed 63 people, including members of the U.S. embassy and CIA. The came after the Western Multinational Force decided to intervene in the Lebanese Civil War.
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San'a, Yemen, September 7, 2008: 19 people died and at least 16 were injured when a group of men disguised at police attacked the outer security rim of the US embassy. Al-Qaeda's affiliate Islamic Jihad of Yemen claimed responsibility.
Kuwait City, Kuwait, Dec 12, 1983: Five killed as a truck rams into the gates of the US embassy and explods.
Teheran, Iran, Nov 4, 1979: The Iran Hostage Crisis as it was known began at 6:30 am when hundreds of Iranian students called the "Muslim Student Followers of the Imam's Line" cut the fence to the U.S. embassy and broke through the gates. They held members of the embassy staff as hostages for 444 days. A disastrous attempted rescue operation resulted in the deaths of 8 American servicemen and one Iranian civilian. The 52 hostages were released on January 20, 1981.
Karachi, Pakistan, June 14, 2002, February 28, 2003, March 15, 2004:The string of bombings outside the US consult in Karachi were in retaliation for the war on terror in Afghanistan, and later Iraq. In all 14 people died and over 100 injured.