A car bomb went off outside a police headquarters in south-eastern Turkey on Sunday, killing one policeman and wounding 23 people, the governor's office said.
Four civilians and 19 police officers were among the injured in the attack in Gaziantep.
The DHA news agency said shots could be heard after the explosion.
German Chancellor Angela Merkel was in Gaziantep on April 23 to visit a camp for Syrian refugees. Gaziantep province borders Syria.
Security measures have been tightened across Turkey on May Day in anticipation of protests.
Meanwhile, three Turkish soldiers were killed and 14 wounded in the in the district of Nusaybin, also in the south-east, in what the military called an "armed attack" by the banned Kurdistan Workers' Party (PKK).
Conflict between the PKK and the state restarted in July last year, after a two-year ceasefire broke down amid mutual recriminations and a collapse of the peace process.