The explosion happened at a military base in the northern border city of Paju, the Ministry of Defence said in a statement, where an artillery unit was conducting a drill simulating live-fire procedures but without real ammunition.

"At approximately 3:24 pm (0624 GMT) Wednesday, a mock training round designed to simulate artillery fire and smoke unexpectedly exploded," the statement said.

The ministry said that at least 10 soldiers were injured, including two who suffered serious burns to their arms and thighs.

Military medics provided first aid at the scene, while fire and rescue authorities sent six ambulances, according to the ministry's statement.

It did not provide any further details but said the cause of the explosion was being investigated.

The Paju base is about 50 kilometres (30 miles) northwest of Seoul, near the heavily fortified border with North Korea, where there are several South Korean military installations.

The two Koreas remain technically at war since their 1950-1953 conflict ended in an armistice and not a peace treaty.

Mandatory military service is required of all men under 30 in South Korea due to long-running tensions with the nuclear-armed North.