A fugitive South Korean solider has been detained after attempting to sneak into China aboard a cargo ship through the western port of Incheon, military and port officials said Thursday.

The 21-year-old sergeant of special forces, whose identity was withheld, covertly entered the port, located west of Seoul, on Saturday after crossing over barbed wire, they said. He then got on board the vessel that was anchored at the port.

After hiding in one of the compartments for more than a day, he was apprehended by a crewman just before the ship was set to arrive at the port of Qingdao, China, on Sunday, they added. He was sent back to Incheon on Tuesday. 

He had also attempted to sneak into the port on Friday but failed, they said.

The arrest comes just a month after another security breach at the port.

In January, two Russians were arrested after attempting to smuggle stolen bikes through Incheon port.

"It is regrettable that such an incident occurred," a port official said, voicing the need to strengthen security measures at one of the country's major facilities. (Yonhaps News)