South Korea's Navy will launch new patrol boats to bolster defense along the tension-prone western maritime sea border with North Korea, the military said Monday.

The Navy will start work to build the 200-ton guided missile and gun armed patrol boats. The boats are updated versions of the Yoon Young-ha-class boats that are already in service with the armed forces.

Seoul is expected to launch some 20 of these patrol killer guided B (PKG-B) boats in the coming years to replace the existing fleet of smaller and less capable Chamsuri-class patrol boats that entered service in the 1970s.

"The new boats are a follow-up to the Yoon Young-ha-class PKG-As, with construction work to start this year," according to the official.

The 440-ton Yoon Young-ha class patrol killers were first deployed along the Northern Limit Line, the de factor sea border with North Korea, in June 2009, under the Patrol Killer Experimental project.

A total of 18 vessels have been launched. Yoon Young-ha, was named after a lieutenant commander who was killed in a maritime skirmish with North Korea in the western NLL in 2002.

The planned deployment of the new boats in the NLL area could significantly enhance the military's operational mobility and ability to respond to North Korean provocations in recent years.

In March 2010, North Korea torpedoed the South Korean Navy corvette Cheonan in the area and 46 sailors were killed or went missing in the incident.

"The new PKG-B vessels will carry lighter weapons and be able to move faster so they could maneuver in the front line area more easily," a Navy official noted. "They will make it easier for us to carry out hit-and-run operations."

For the weapons system, the boats will carry guided missiles which are currently under development, according to the military.

The forthcoming patrol killers will be half the size of the currently deployed vessels that measure some 63 meters in length and 9 m in width with a capacity to accommodate around 40 sailors. (Yonhap)