SEOUL, South Korea -- North Korea has replaced its defence minister with a hardline military commander believed responsible for deadly attacks on South Korea in 2010, diplomats in Pyongyang said Thursday. It is the latest in a series of high-profile appointments leader Kim Jong Un has made since he took power nearly a year ago.

Diplomats in Pyongyang told the Associated Press that they were informed that Kim Jong Gak had been replaced as armed forces minister by Kim Kyok Sik, commander of the battalions linked to two deadly attacks in 2010 blamed on North Korea.

The diplomats declined to be named, saying they had not been cleared to discuss the matter with the media.

South Korean officials said they also received similar information about the North Korean personnel changes but gave no further details. The officials spoke on condition of anonymity, citing government protocol.

The move comes amid speculation that North Korea may be preparing a long-range rocket launch. An April launch that broke apart after liftoff drew UN condemnation and deepened animosity between the Koreas. North Korea says its launches are meant to put a satellite into orbit.

Analysts say Kim Jong Un aims to use the personnel change to bolster his grip on the 1.2 million-member military, which forms the backbone of his rule over the country.

Kim Jong Un is trying to put his stamp on the military by building loyalty with troops and also by creating tension among generals through personnel changes, said Baek Seung-joo, an analyst at the state-run Korea Institute for Defence Analyses in Seoul.

The appointment of a hawkish general could also mean North Korea wants to show a tough face to Washington and Seoul, said analyst Hong Hyun-ik at the private Sejong Institute in South Korea.

The new defence minister, Kim Kyok Sik, formerly served as North Korea's military chief and as commander of the units blamed in the 2010 attacks. North Korea acknowledges an artillery bombardment of a South Korean island that killed four South Koreans but denies any role in an explosion that sank a South Korean warship that year, killing 46.

Kim is North Korea's third defence minister since Kim Jong Un took power after his father Kim Jong Il's death in December.

Previous defence chief Kim Jong Gak had been considered a trusted aide of Kim Jong Un. He was made a vice marshal in February and appointed defence minister in April. He was also one of seven men accompanying Kim Jong Un as he walked alongside a limousine bearing Kim Jong Il's coffin during his December funeral.

It's not the first time Kim Jong Un has made high-level personnel appointments.

In July, Kim dismissed military chief Ri Yong Ho, who was seen as one of his key mentors, and named little-known vice marshal Hyon Yong Chol as his new General Staff chief.

In April, Kim also reshuffled top Workers' Party posts by taking on top party posts held by his father and giving other high-level posts to close associates.

In recent months, North Korea has also reshuffled top Cabinet members such as the ministers of sports, electronics industry and agriculture, according to Pyongyang's official Korean Central News Agency.