Several people have been injured in an explosion at a riot police headquarters in the Turkish city of Diyarbakir.

A police source said the explosion appeared to have taken place in a vehicle repair section of the police compound, causing part of the roof to collapse and wounding at least four people.

The explosion could be heard in several areas of the city.

The blast comes days before a referendum on broadening President Recep Tayyip Erodgan’s powers, which critics claim would drag the country towards becoming an autocracy.

The explosion was in the central, largely residential district of Baglar, where a car bombing by suspected Kurdistan Workers Party (PKK) militants wounded scores of people last November.

#diyarbakır #patlama olay yeri görüntüsü diyarbakır pic.twitter.com/JNzKxkxQOS

— Hakan Yılmaz (@hymedya) April 11, 2017

#diyarbakır#patlama anı güvenlik kamerası görüntüsü. patlama anı. diyarbakır pic.twitter.com/R9SmQ4GAL2 — Hakan Yılmaz (@hymedya) April 11, 2017

First footage of #Diyarbakir blast, targeted a Police station. pic.twitter.com/84M6tOhbOJ

— Barzan Sadiq (@BarzanSadiq) April 11, 2017