A radical Turkish Marxist group has claimed responsibility for the suicide bomb attack at the US embassy in Ankara, according to a statement posted on the internet on Saturday.
The Revolutionary People's Liberation Front (DHKP-C), which the Turkish authorities had already blamed for Friday's bombing, accused the United States of being the "murderers of the world", according to a statement on the Halkin Sesi (The Voice of the People) website.
The site carried two pictures of the bomber identified as Alisan Sanli, one of which shows him brandishing a gun.
The authorities have said the bomber was previously jailed for his involvement in an attack on a military compound in Istanbul in 1997.
A Turkish guard at the embassy in an affluent area of Ankara was killed in the attack and three other people were wounded.
Friday's blast came as John Kerry replaced Hillary Clinton's tenure US secretary of state.
As she stepped down, Clinton referred to the Ankara attack, the second against a US diplomatic facility in less than five months, saying: "Of course, we live in very complex and even dangerous times, as we saw again just today at our embassy in Ankara, where we were attacked and lost one of our foreign service nationals, and others injured."
In September heavily armed militants linked to al Qaeda overran the US consultate in Benghazi, Libya, killing US Ambassador Chris Stevens and three other Americans.
"I know that the world we are trying to help bring into being in the 21st century will have many difficult days," Clinton said Friday.
The statement by the DHKP-C highlighted the vulnerability of America's 70,000 diplomats, mocking US assurances that its embassies have the tighest security in the world.
The group also threatened further attacks on other US diplomatic facilities in Turkey.
Sanli, who was earlier named by officials as Ecevit Alisan Sanli, blew himself up Friday at the first checkpoint on the perimeter of the embassy compound, detonating a hand grenade and about six kilogrammes (13 pounds) of TNT, the Ankara governor's office said in a statement.
He had previously been jailed after a 1997 attack at a military compound in Istanbul and released in 2001.
He left Turkey after his release from prison but later returned using false papers, Interior Minister Muammer Guler said.
According to local press reports, Sanli took part in a hunger strike during his time in detention which caused him to suffer from Wernicke-Korsakoff syndrome, a brain disorder caused by thiamine deficiency.
He was chosen for the suicide attack because "his days were numbered," according to the dailies Milliyet and Vatan.
The United States, Britain and France all swiftly condemned the attack while Turkey's foreign ministry slammed a "hostile act of terror targeting democratic values defended by Turkey, the United States and other allies."
Meanwhile Nato secretary general Anders Fogh Rasmussen denounced the "outrageous attack on the diplomatic premises of one ally, on the territory of another ally."
The outlawed DHKP-C, blacklisted by the United States and the European Union as a terrorist group, has waged a string of attacks over the past few decades that have left dozens of people dead, including prominent political and military figures.