ANKARA, Turkey – A suicide bomber struck the American Embassy in Ankara on Friday, killing a Turkish security guard in the second deadly assault on a U.S. diplomatic post in five months.

Washington immediately warned Americans to stay away from all U.S. diplomatic facilities in Turkey and to be wary in large crowds.

The attack drew condemnation from Turkey, the United States, Britain and other nations and officials from both Turkey and the United States pledged to work together to fight terrorism.

“We strongly condemn what was a suicide attack against our embassy in Ankara, which took place at the embassy’s outer security perimeter,” White House spokesman Jay Carney said.

“A suicide bombing on the perimeter of an embassy is by definition an act of terror,” he said. “It is a terrorist attack.”

Turkish Prime Minister Recep Tayyip Erdogan said police believe the bomber was connected to a domestic leftist militant group. Carney, however, said the motive for the attack and who was behind it was not known.

A Turkish TV journalist was seriously wounded in the 1:15 p.m. blast in the Turkish capital, and two other guards had lighter wounds, officials said.

The Anadolu Agency identified the bomber as Ecevit Sanli. It said the 40-year-old Turkish man was a member of the outlawed Revolutionary People’s Liberation Party-Front, or DHKP-C, which has claimed responsibility for assassinations and bombings since the 1970s.

The group has been designated a terrorist organization by the United States but had been relatively quiet in recent years.

Hillary Rodham Clinton, in her farewell speech to State Department staff moments after she formally resigned as secretary of state, said “we were attacked and lost one of our foreign service nationals.”

On Sept. 11, 2012, terrorists attacked a U.S. mission in Benghazi, Libya, killing U.S. Ambassador Chris Stevens and three other Americans.