PAJU, Gyeonggi Province -- A fire broke out in North Korea on Monday and was rapidly spreading to the South Korean side of the inter-Korean border, South Korean authorities said.

The blaze started at around 11 a.m. near a North Korean guard post located about 600 meters north of the Demilitarized Zone, military officials said.

By 3:45 p.m., it had spread close to the Dora Observatory in Paju, north of Seoul, a popular tourist destination.

The observatory was closed to visitors on the day, and no casualties or damage was reported, officials added.

More than 50 South Korean firefighters were putting out the fire, Paju city and military officials said, adding that three helicopters were awaiting the approval of the United Nations Command to aid in the process.

The cause of the fire was unknown, according to an official at the South Korean Joint Chiefs of Staff.

Authorities have also restricted access to the customs office leading to the South Korea-run industrial complex in the North’s border town of Gaeseong.

The Korean DMZ, the world’s most heavily-armed border, runs the width of the Korean Peninsula roughly along the 38th parallel. It is guarded by more than 2 million troops on both sides.

(Yonhap)