South Korea has received intelligence suggesting North Korea is trying to assassinate its defence chief, the Yonhap news agency reported Wednesday, citing government sources.

Following the new threat, Defence Minister Kim Kwan-jin, who is known for his hard stance against Pyongyang has now increased his security entourage and is now escorted by military personnel in order to prevent any assassination attempts.

"The defence minister is a key official and we're always keeping close tabs on his security," one source said. "When he has to leave the office for functions and other commitments, we do take extra care."

Military and intelligence officials were reportedly still trying to work out whether would-be assassins could be North Korean agents or other foreign nationals sent by Pyongyang, another source said.

Kim, who is a former army general, became the Defence Minister last December and has been a vigorous critic of North Korea.

Ridiculing the claims however, Pyongyang's state media, responded to the allegations by calling Kim Kwan-jin an "anti-North Korea confrontation maniac."

The new claim came as South Korea said the North had open fire near the Northern Limit Line in the Yellow Sea, prompting the South to attack back and confirm that three shells were fired back. Both sides' shells landed in the water, and there were no reports of casualties, Kim South Korea Defence Ministry spokesman Kim Min-Min-seok added.

To read more on the subject please click here: North and South Korea Exchange Fire Over Yellow Sea Dispute