In Istanbul, police backed by helicopters arrested at least 20 people suspected of having links to the banned Kurdistan Workers' Party, or PKK.
Istanbul's anti-terrorism directorate said there were lawyers among those detained, the Associated Press reported.
Wednesday's raids come after President Recep Tayyip Erdogan said Turkey would "redefine" terrorism and terrorists so that legal action can be expanded against anyone supporting terrorism including legislators, academics and journalists.
No group has claimed responsibility for the attack on Sunday, which killed 37 people.