An explosion at a plant run by South Korean defense firm Hanwha Aerospace killed five people on Monday, local fire authorities said, with two others injured.

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

Hanwha Aerospace is a major South Korean defense 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, and produces large propulsion engines and handles rocket propellants.

A representative of the Daejeon Fire Headquarters said that five people died and two others were injured.

Authorities were unable to obtain the factory’s layout since it is protected under national security laws, an official said at the briefing.

“The exact circumstances and extent of the damage have not yet been fully determined. The fire has not yet been completely extinguished,” a Hanwha representative said, adding the company was investigating the incident.

South Korean President Lee Jae Myung called for the mobilization of all available resources to respond to the accident and for an investigation. (AFP)