ANKARA: A far-leftist suicide bomber killed a Turkish security guard at the U.S. Embassy in Ankara Friday, officials said, blowing open an entrance and sending debris flying through the air.

The attacker detonated explosives strapped to his body after entering an embassy gatehouse. The blast could be heard a mile away.

Several U.S. and Turkish staff at the embassy were struck by debris, U.S. State Department spokeswoman Victoria Nuland said.

The spokeswoman said a Turkish visitor to the embassy was in “serious condition” following the blast, which Turkish Interior Minister Muammer Guler said was carried out by a member of an illegal far-left group. Nuland said the staff members struck by debris were treated at the embassy clinic and released.

The White House said the suicide attack was an “act of terror,” but the motivation was unclear.

Islamist radicals, extreme left-wing groups, ultra-nationalists and Kurdish militants have all carried out attacks in Turkey in the past. There was no claim of responsibility. “The suicide bomber was ripped apart and one or two citizens from the special security team passed away,” said Prime Minister Recep Tayyip Erdogan, who was attending a ceremony in Istanbul when the blast happened.

“This event shows that we need to fight together everywhere in the world against these terrorist elements,” he added.

Turkish media reports identified the bomber as Ecevit Sanli, a member of the Revolutionary People’s Liberation Party-Front (DHKP-C) leftist group, who was involved in attacks on a police station and a military staff college in Istanbul in 1997.

The DHKP-C opposes what it considers as U.S. influence over Turkish foreign policy.

U.S. Ambassador Francis Ricciardone emerged through the main gate of the embassy, which is surrounded by high walls, shortly after the explosion to address reporters, flanked by a security detail as a Turkish police helicopter hovered overhead.

“We’re very sad of course that we lost one of our Turkish guards at the gate,” Ricciardone said, describing the victim as a “hero” and thanking Turkish authorities for a prompt response.

A U.S. national security source said U.S. officials believed the incident was a suicide bombing but added that security measures had worked properly, in that the attacker was not able to get past the outer perimeter of the compound and neither the embassy buildings were damaged, nor were U.S. personnel injured.

It was the second attack on a U.S. mission in four months. On Sept. 11, 2012, U.S. Ambassador Christopher Stevens and three American personnel were killed in an attack on the U.S. Consulate in Benghazi, Libya.

A well-known Turkish journalist, Didem Tuncay, who was on her way in to the embassy to meet Ricciardone when the attack took place, was in a critical condition in hospital.

The DHKP-C, deemed a terrorist organization by both the United States and Turkey, has been blamed for suicide attacks in the past, including one in 2001 that killed two police officers and a tourist in Istanbul’s central Taksim Square.

Guler said the bomber could have been from the DHKP-C which has carried out a series of deadly attacks on police stations in the last six months, or a similar group.

The attack may have come in retaliation for an operation against the DHKP-C last month in which Turkish police detained 85 people. A court subsequently remanded 38 of them in custody over links to the group.