The explosion was reported to authorities at around 11am at Hanwha’s plant in Daejeon, about 150km south of Seoul.

A representative of the Daejeon Fire Headquarters told AFP that five people have died and two others were injured, without providing further details.

The blast is believed to have happened inside the factory according to authorities speaking with Yonhap news agency.

Hanwha Aerospace is a major South Korean defence manufacturer which produces weapons, artillery systems and aerospace components.

Its Daejeon facility focuses on research and development, including advanced weapons technologies and space-related systems.

A Hanwha representative told AFP “the exact circumstances and extent of the damage have not yet been fully determined.

The fire has not yet been completely extinguished”.

“President Lee Jae Myung instructed officials to mobilise all available resources to bring the fire under control,” his office said.