Four people were killed and around 100 injured in an explosion that rocked a fireworks factory in northwestern Turkey on Friday, the Turkish health minister said.

The government's disaster agency AFAD called the explosion an "industrial accident" in the district of Hendek in Sakarya province.

"As of right now, four people have died... and 97 people injured were taken to hospital," Health Minister Fahrettin Koca said. Sixteen of them were swiftly discharged from hospital, he added.

Interior Minister Suleyman Soylu said three factory workers were still missing, adding that the resultant fire had been brought under control.

The ministers had been dispatched to the province by President Recep Tayyip Erdogan.

Images on television earlier in the day showed a dark grey plume of smoke with sparks visible, a result of fireworks going off inside the building.

Provincial governor Cetin Oktay Kaldirim said up to 200 people were inside the factory at the time of the explosion, the official Anadolu news agency reported.

Hendek mayor Turgut Babaoglu said many workers escaped the building during the incident.

Dozens of firefighters and rescue workers were mobilised after the explosion around 0815 GMT.

The HaberTurk broadcaster's website reported there had previously been explosions at the factory in 2009, 2011 and 2014. One person died in the incident in 2014, the website added.