Seoul, Dec 21 (IANS): South Korea on Thursday fired warning shots towards North Korea as Pyongyang's forces were trying to locate a soldier who crossed the border and defected to the South earlier in the day, a Defence Ministry spokesman said here.

The South Korean military first issued a warning through its loudspeakers when it saw a group of North Korean border guards approach the Military Demarcation Line, the effective border line between the two countries, the spokesman told Efe news.

As North Korea apparently ignored the warning, several shots were fired, the spokesman said, adding that North Korea's border patrol then decided to back down.

Shortly afterwards, the South Korean troops heard several warning shots coming from the North.

The North Korean soldier appeared in front of a South Korean border guard post at 8.04 a.m. after having crossed the western side of the border.

This is the fourth North Korean soldier to defect to the South this year.

The soldier was the first one since the dramatic defection of a trooper who was shot five times by the North Korean army on November 13 during his escape through the Joint Security Area, the only border area where soldiers of the two countries are stationed face to face.

The defections have triggered tensions along the border line of the two countries.