A group called the Turkish Revenge Brigade has claimed responsibility for a bomb blast in the Kurdish-populated city of Diyarbakir that killed 10 people late Tuesday.
A statement posted on the group's website threatened to kill 10 Kurds for every Turk killed in attacks by rebels of the Kurdistan Workers Party, or PKK.
The claim cannot be independently verified.
Meanwhile, a special U.S. envoy, retired General Joseph Ralston, held talks with Turkish officials in Ankara Wednesday on countering Kurdish rebels who fight Turkey from bases in Iraq.
Ralston said urgent, visible measures are needed to show the Turkish, American and Iraqi public that officials are serious about eliminating the threat of terrorism.
Another Kurdish group fighting Turkey, the Kurdistan Freedom Falcons, claimed responsibility for a string of bombings last month in Mediterranean tourist resorts in Turkey, including one that killed three people.
More than 30,000 people have been killed since the PKK took up arms in 1984.
Some information for this report was provided by AP.