Image caption New premier Choe Yong-rim is Pyongyang's party chief

North Korea has reshuffled its top leadership at a rare second session of its parliament, state media says.

Top leader Kim Jong-il attended the session, KCNA news agency said, after missing the previous one on 9 April.

Choe Yong-rim replaced Kim Yong-il as premier - the official responsible for the communist state's economic policy.

State media also said that Mr Kim's brother-in-law, Chang Song-taek, was promoted to a powerful military post on the National Defence Commission.

Mr Chang is thought to be a backer of a hereditary succession involving Mr Kim's youngest son, Kim Jong-un.

Succession hint?

The 687-member parliament - known as the Supreme People's Assembly - usually meets just once a year.

The special session of parliament, announced on 18 May, was called to discuss "organisational matters", KCNA said.

Choe Yong-rim, the Pyongyang party chief, was reportedly proposed as premier by the political bureau of the party's Central Committee.

Some reports linked the replacement of the premier to last year's failed currency revaluation.

Mr Chang's promotion came "at the proposal of Kim Jong-il", the agency said.

The NDC is North Korea's highest military body and Mr Chang - already a member - now becomes a vice-chairman.

Mr Chang has been described as one of Mr Kim's most trusted allies. Some reports said he had overseen affairs while Mr Kim was incapacitated after a stroke in 2008.

His promotion will be seen by some as a sign that Mr Kim is putting key personnel in place to ensure a smooth transition of power to his son.

Three ministers - of light industry, foodstuffs and physical culture - were replaced, and six new vice-premiers appointed.

The reshuffle comes with inter-Korean ties in tatters, following the sinking of a South Korean warship.

Forty-six sailors were killed when the Cheonan went down on 26 March near the disputed inter-Korean border.

International investigators say a torpedo fired from a North Korean submarine sank the ship - something Pyongyang rejects.

It has called Seoul's decision to refer the issue to the UN Security Council "intolerable".