The Cheonan case was one of the biggest turning points in inter-Korean relations.

The Lee government imposed a package of tough economic sanctions on Pyongyang, effectively suspending all inter-Korean joint projects except for the Kaesong Industrial Complex.

The current Park Geun-hye administration maintains that the North should first take a responsible measure in connection with the Cheonan incident if it wants to see the sanctions, dubbed the May 24th Measure, lifted.

The South has been putting more pressure on the North as it marks the fifth anniversary of the March 26 tragedy this week.

The North's commission, however, argued that the South "cooked up" the Cheonan story in a bid to nullify the two inter-Korean summit deals in 2000 and 2007.

"The warship sinking case and the 'May 24 step' taken by them in its wake were a vivid manifestation of the anti-reunification acts," said the policy department of the organ directly headed by leader Kim Jong-un.

It urged the South to immediately lift the sanctions, saying they are "based on the fictitious story about the North's 'involvement' in the sinking."

"If the South Korean authorities truly wish for the improvement of the North-South relations, they should bear in mind that they have to move first to lift the measure," it added.

The commission also demanded a re-investigation into the Cheonan sinking, calling on the South to reveal all related evidence associated with it.

The South dismissed the North's statement and urged it to stop "distorting" relevant facts.

"It was clearly found through an international probe that the Cheonan sinking was done by North Korea," a unification ministry official told reporters, saying it's the government's formal position.

It's regrettable that Pyongyang is still condemning the South by distorting what actually happened, he added.

The official made it clear that the North should take a sincere step to address the Cheonan issue in order for the May 24th Measure to be lifted. (Yonhap)