Last night, near the Candan Ercetin concert (part of Mersin Festivali) on Cumhuriyet Meydani, a bomb exploded under a police vehicle, injuring several people. I was in Adana at the time and didn't find out about the bomb until this morning. At the moment, police don't know who undertook the bombing. The money is on either leftist, Kurdish or Islamist militant groups.
Following are a few news links. Some have graphic photos of the injured, so be warned.
BBC News (no photos)
Reuters (small photo)
Xinhuanet (graphic photos)
AFP via TurkishPress.com (graphic photo)
Ledge-Enquirer via AP (no photos, post-incident analysis)