The foreign ministry has issued a travel ban on war-torn Sudan effective as of Friday midnight.

Under the Level 4 travel alert, the highest in a four-tier system, South Koreans are banned from visiting all areas of the African nation which is reeling from escalating military conflict.

The ministry said it was deemed necessary to ban travel or stay in Sudan to protect citizens amid continued fighting between the Sudanese Armed Forces and the paramilitary Rapid Support Forces with rising instability, casualties and refugees.

The ministry said the previous Level 3 alert has been raised to the highest level and asked South Koreans to cancel any travel plans. Violators can face criminal punishment under the passport law.

The four-tier alert system comprises "caution," "restraint," "evacuation recommended" and an all-out travel ban.