(CNN) -- Turkish officials say a suicide bomber belonging to a radical leftist organization blew himself up just outside the U.S. Embassy in Ankara on Friday.
The blast killed a Turkish security guard. A senior U.S. official said no Americans were wounded.
Istanbul police identified the bomber as Ecevit Shanli, a member of DHKP-C, a Marxist Leninist terror group.
Hasan Selim Ozertem, a security expert at the International Strategic Research Organization in Ankara, said the attack could be related to arrests of a number of DHKP-C members two weeks ago.
Since the beginning of January, 85 members of the group have been arrested, he said, adding that Turkish police have been closely focusing on the group over the past five years. The DHKP-C was established in the 1970s.
Ozertem said that one plausible theory is the group is trying to send a message to Turkish authorities by attacking the U.S. Embassy because the building is near the Turkish parliament.
DHKP-C has a track record as a "subcontractor" group for other militant outfits, but it is also believed to have relationships with states in the region such as Syria and Iran, Ozertem said. The group also has a relationship with the PKK, the Kurdistan Workers Party, which has been warring with the Turkish government for some time.
Ozertem said that the attack could be linked to negotiations between the PKK and Turkish government, or that Syria or Iran could be involved considering the recent deployment of Patriot missiles in Turkey as a defense against possible missiles from Syria. He said he is unaware of any direct link between DHKP-C and al Qaeda.
At the chaotic scene at the embassy, there were conflicting accounts of how many people were wounded.
Ankara police and health officials said two were injured, while Ankara Gov. Aladdin Yuksel said one person was hurt.
Earlier Friday, U.S. State Department spokeswoman Victoria Nuland said that a "terrorist blast" happened at 1:13 p.m. at a checkpoint on the perimeter of the embassy.
"We are working closely with the Turkish national police to make a full assessment of the damage and the casualties, and to begin an investigation," she said.
The FBI will investigate the bombing along with local authorities, a U.S. law enforcement official told CNN. The FBI has a legal attache office in Ankara, in the U.S. Embassy, the FBI's website says.
Images from CNN sister network CNN Turk showed a hole in what appeared to be a building that is part of the outer gate of the embassy compound, which is in a very well-protected area of Ankara near the Turkish parliament building.
The gated complex includes blast doors, reinforced windows and a series of metal detectors that visitors must navigate before reaching embassy offices.
The blast happened on the same day that Secretary of State Hillary Clinton is leaving her job. Sen. John Kerry will fill that role amid widespread discussion at the department over security at its global posts following last year's attack on the U.S. post in Benghazi, Libya.
Republican Rep. Ed Royce, chairman of the House Foreign Affairs Committee, issued a statement saying that Friday's bombing is "yet another stark reminder of the constant terrorist threat against U.S. facilities, personnel and interests abroad."
"Coming after Benghazi, it underscores the need for a comprehensive review of security at our diplomatic posts," his statement said. "The committee stands ready to assist the State Department in protecting our diplomats."
Vice President Joe Biden, in Europe to discuss issues such as Syria's civil war, spoke to reporters along with German Chancellor Angela Merkel, who said she is "very sad that there was an assault on the U.S. Embassy in Ankara. ... I want to send my condolences to everyone involved."
French Foreign Minister Laurent Fabius also condemned the attack and sent condolences.
Biden said he appreciated the sympathy. "I don't have much detail to tell, but it was characterized by our mission as a terrorist attack on our embassy in Ankara," he said. "To the best of our knowledge, there were some injured. ... We don't have the details yet."
Turkish Prime Minster Recep Tayyip Erdogan said the blast was an attack "against the peace and welfare of our country."
Turkey has seen numerous acts of political violence in the past from groups such as leftist anarchists, Kurdish separatists, Islamists and al Qaeda. Turkey has also backed rebels in neighboring Syria, and some violence from that conflict has spilled over the border.
The explosion occurred as about 400 U.S. military personnel are moving Patriot missile defense equipment to a Turkish base as part of an effort to defend the country from possible attack from Syria. The first battery became operational last Saturday in the city of Adana, NATO said, and more equipment arrived Wednesday in the port city of Iskenderun.
The British Embassy in Ankara strongly urged citizens to avoid areas around the U.S. Embassy.
The U.S. Embassy posted a message on its website thanking "the Turkish government, the media, and members of the public for their expressions of solidarity and outrage over the incident."
While the U.S. Embassy in Ankara has not seen this kind of incident in decades, in 2008 three police officers died in a shootout with assailants outside the U.S. Consulate in Istanbul.
Three attackers also died in the incident, which the U.S. ambassador at the time called "an obvious act of terrorism."
One of the attackers in that incident was believed to have trained with al Qaeda in Pakistan's Waziristan region.