The secretary general of the city municipality has given the information to the media.
At least four people are thought to have been killed.
The state-run Anadolu news agency says police shot dead two attackers after the blast.
They are actively looking for a third.
Hospital sources in Izmir have told reporters ten people have been brought in wounded following the explosion. (Euronews)
Atentado con coche bomba en Turquía https://t.co/LIslfXcLw6 pic.twitter.com/Ks8wNgaeTk
— Luis Carballo (@LCEuronews) 5 gennaio 2017
İzmir Adliyesi C Kapısı Polis noktası önünde bombalı aracın patlama anı#İzmir pic.twitter.com/NbBQsxjhT0
— TÜRK Polisi Ϝ ϓ ſ Ϟ (@TurkPolisiTC) 5 gennaio 2017