Authorities in Seoul say the fire started Monday on a farm on the north side of the frontier and quickly spread along an access road, in what is usually a restricted area across from the 4 kilometer-wide (2.4 miles) demilitarized zone (DMZ).

"Due to strong winds, it has spread quickly through the DMZ," an unnamed ministry spokesman told Reuters.

The heavily armed DMZ has divided Korea in two since the 1950-53 Korean War. Troops from both sides face each other as the two sides are still technically at war.

But the rival nations appeared focused on containing the blaze before it could threaten buildings in a jointly-managed industrial zone where scores of personnel from South Korea remain trapped.

"Both sides are now trying to control the blaze after blocking access to the Kaesong industrial park," an unnamed ministry official told AFP.

South Korea has sent at least 11 fire trucks, seven helicopters and about 50 firefighters to try and contain the blaze. North Korean crews are also reportedly assisting the effort.

No casualties have been reported and the cause has not been released.

More than 50,000 North Koreans work at 125 firms from South Korea at the Kaesong complex. The jointly-managed industrial center was opened in 2004 as a symbol of cross-border cooperation.

Disputes are not uncommon between the two Koreas. Earlier this month a row erupted after North Korea announced wage hikes for workers. South Korea argues the announcement is illegal as it circumvented the joint committee that administers the industrial zone.

jar/jr (AFP, dpa, Reuters)