North Korea moved closer to a hereditary succession by making a brother-in-law of aging leader Kim Jong Il a vice chairman of the powerful National Defense Commission.

The country's 687-seat parliament meeting in an extraordinary session promoted Jang Song Thaek, 63, to a leadership position of the country's top military body, the state-run media Korean Central News Agency said.

Jang, already a member of the defense commission, is believed to back a hereditary succession to Kim Jong Il, 68, who is in believed to be in frail health after a possible stroke in 2008. His youngest of three sons, Kim Jong Un, 27, is being groomed for eventually stepping into his father's shoes.

Kim Jong Un is thought to be the head of the ruling Korean Workers' Party. South Korea's National Intelligence Service says it believes Kim Jong Un will officially be declared leader in 2012.

The previous session of the Supreme People's Assembly, which meets usually once a year, was April 9. But in May it was announced an extraordinary session was planned for early June to settle "organizational matters," KCNA said.

Kim Jong Il was at the session and reported to have requested that Jang become a vice chairman of the defense commission, the KCNA said.

"Jang is now in the most favorable position to take over the country should Kim become incapacitated," Koh Yu Hwan, a North Korean professor at Seoul's Dongguk University, told the South Korean news agency Yonhap. "He'll head the oligarchy and guide Jong Un."

Also during the parliament's session, Choe Yong Rim was announced as the new premier, replacing Kim Yong Il. Choe, the party chief of the capital city Pyongyang, is responsible for the communist state's economic policy.

The reshuffle included replacing the ministers of light industry, foodstuffs and physical culture and also appointing six new vice premiers.

The appointments come as the isolated, economically struggling Communist country stands accused of sinking a South Korean warship in March, further escalating the already tense situation on the Korean Peninsula.

An independent international investigation team concluded late last month that it was a North Korean torpedo sank the 1,200-ton South Korean Cheonan in the Yellow Sea on March 26, killing 46 sailors.

North Korea has consistently denied it had anything to do with the sinking, accusing South Korea and its close ally the United States of blatant propaganda.

Jang met the youngest sister of Kim Jong Il while they were at university and married two years later. They had one child, Jang Keum Song, but she is reported to have committed suicide in Paris died in 2007 over a love affair.

Jang worked his way up the Communist party organizational ladder and was elected in 1992 to the party's ruling Central Committee.

However, in mid 2004 Jang was mentioned less and less in North Korean media. This led many watchers of the North's politics to suspect that Jang's enemies within the Communist party had succeeded in isolating him despite his influence with his brother-in-law, the national leader Kim Jong Il.

After reappearing in 2006 Jang has been seen often at Kim's side and has accompanied him on dozens of visits around the country every year, a spokesman for South Korea's Unification Ministry said.

Jang's appointment as a vice chairman is significant because he is a party person steeped in administration and management and isn't a military official, Daniel Pinkston, an analyst for International Crisis Group said.

He is one of more than a dozen administrators rising in power within the military organization. This may signal a shift toward the National Defense Commission taking on a wider administrative role and not be solely focused on military issues, Pinkston said.

The influence of party apparatchiks on military thinking may help to instill some real politic into inter-Korean affairs given the continuing fallout from the Cheonan incident and more threats of international sanctions.

Even North Korea's main ally China is said to be losing patience with Pyongyang.

China has consistently called for calm on all sides over the incident. But it also has said North Korea must come up with more than just statements of denial and propaganda slogans if it wants to convince an increasingly angry international community of its innocence.