The suicide bombing in Ankara Friday is a reminder to counterterrorism agencies that it's not just jihadist groups who threaten Western governments and their interests overseas. Pockets of the extreme left and extreme right still consider political violence legitimate -- among them the Revolutionary People's Liberation Party in Turkey.
Turkish authorities have blamed the U.S. Embassy attack on the group, better known as DHKP-C, and are in the process of identifying the bomber.
Analysts say it is likely the attack had two aims -- to embarrass the Turkish government and to demonstrate the group's hostility to the deployment of Patriot anti-missile batteries on Turkish soil. Several members of the group are thought to be close to the Syrian regime.
DHKP-C has a relationship with the Turkish Kurdish separatist group PKK, which is also close to the Syrian government. About one-third of the PKK's fighters are said to be Syrian, according to regional analysts.
DHKP-C is viscerally hostile to the Turkish state, the United States and NATO, and has had links with the far-left in Europe.
In recent days, Turkish police have arrested several dozen people suspected of links with DHKP-C, among them a number of lawyers. However, Human Rights Watch called the arrests an "arbitrary and abusive use of anti-terrorism laws in Turkey."
Turkish authorities believe the suicide bomber Friday was Ecevit Sanli, a longtime member of the group. DNA tests are being conducted to confirm his identity.
Sanli received bomb-making training somewhere in Europe in the mid-1990s, according to Hasa Selim Ozertem, a security expert at the International Strategic Research Organization in Ankara. Turkish officials say that as a result of counterterrorism operations on Turkish soil, DHKP-C became increasingly active among the Turkish diaspora in Europe.
Sanli returned to Turkey in 1997 and was subsequently involved in attacks on the Istanbul police headquarters and senior military officials using anti-tank weapons. After being arrested, Sanli went on a lengthy hunger strike and was released from jail in 2002 because of a neurological disorder.
DHKP-C has been active for more than 30 years and espouses a Marxist-Leninist philosophy reminiscent of the Cold War. It grew out of another far-left group, Devrimci Sol (Revolutionary Left), formed when Turkey was in political turmoil, with clashes between militant left- and right-wing groups undermining a weak political system. Devrimci Sol claimed responsibility for gun attacks that killed two Americans, including a U.S. military employee, and an attack that wounded a U.S. military officer in early 1991 in protest of the Gulf War.
Among other attacks attributed to the DHKP-C was the assassination of a former justice minister, Mehmet Topac, in 1994, as well as the murders of a number of senior police and military officials and, 1996, a prominent businessman, Ozdemir Sabanci.
Among its more recent operations was an attempt to kill another former justice minister, Hikmet Sami Turk, in 2009. The female suicide bomber's main explosive charge did not go off.
Security analysts say the latest attack is very similar to one launched on an Istanbul police station last year. Again, a former hunger striker who was critically sick with cancer arrived at the police station wearing a belt stuffed with explosives and triggered the bomb just before passing through an X-ray machine.
Ozertem told CNN he is unaware of any links between DHKP-C and al Qaeda-type actors, but the possibility can't be entirely dismissed because al Qaeda sympathizers have become increasingly active in the region.
The Turkish National Police assessment of the group says, "American, European and Israeli companies and enterprises are also among the targets of DHKP-C since they are considered by the terrorist organization as assets of global imperialism."
It says the group is also involved in drug trafficking to finance its operations.
Analysts consulted by CNN do not believe the organization has the capacity to launch a sustained terrorist campaign, nor penetrate security at well-guarded installations. Its last known attack aimed at a U.S. target in Turkey was in 1999, when two men tried to fire a rocket at the U.S. Consulate General building in Istanbul. Both were killed in a subsequent firefight.