The explosion happened close to restaurants in the centre of the Mediterranean city of Antalya.
This blast came hours after three bombs hit another coastal resort, Marmaris, injuring at least 21 people.
The Turkish economy is heavily reliant on tourism, which Kurdish separatists have repeatedly threatened to target.
No-one has claimed responsibility for carrying out the attack in Antalya, but a Kurdish militant group is purported to have said it was behind Sunday's blasts in Marmaris and Istanbul.
The Kurdistan Freedom Falcons (Tak), which has links to the banned separatist Kurdistan Workers Party (PKK), claimed responsibility on its website. The claims have not yet been verified.
The latest blast occurred near to a building housing local restaurants, a spokeswoman for the governor's office in Antalya said.
The area around the scene was cordoned off as the police investigation got under way, the BBC's Sarah Rainsford said.
The explosion happened just before 1700 local time.
Local police were quoted as saying two people had died. Turkish NTV television reported that a third person had died in hospital from their injuries.
CNN-Turk television reported that 20 people had been injured.
A shaken local businessman told Reuters news agency "a parked motorbike.. had exploded and pieces of the motorbike were scattered all around". He said a street vendor had died.
Whatever the cause of the blast, this latest incident has only added to an already nervous atmosphere, our correspondent says.
Wave of bombings
Most of those injured in Marmaris - including 10 Britons - were on a minibus ferrying local people and holidaymakers along the main street.
Istanbul was also hit by a bomb attack on Sunday night, when a roadside device exploded injuring six Turkish nationals.
Both Marmaris and Antalya are popular with European and Russian holidaymakers.
The attacks are the latest in a wave of similar bombings in Turkey in recent years, blamed on either Kurdish separatists, Islamic militants or left-wing extremists.
Four people - including three foreigners - were killed in an explosion in Antalya in June. Initial investigations suggest a gas canister exploded, but doubt was cast over whether it had been an accident.