North Korea said Saturday new leader Kim Jong-Un has formally been appointed supreme military commander, another sign he is tightening his grip on power, as it renewed vitriolic attacks on Seoul.

Jong-Un had already been declared "supreme leader" of the country during memorial ceremonies for his late father Kim Jong-Il on Thursday, as the nation ended 13 days of mourning.

North Korea warned the world Friday to expect no policy changes under new leader Kim Jong-Un, and threatened retaliation against South Korea for "rubbing salt" into the wounds of its grieving people.

The tough statement came a day after the communist nation ended 13 days of mourning for late leader Kim Jong-Il, and proclaimed his son Jong-Un as new supreme chief at a massive memorial ceremony.

North Korea staged a massive memorial service for Kim Jong-Il on Thursday to end 13 days of official mourning, and formally declared his untested young son Jong-Un as the new supreme leader.

Addressing tens of thousands of troops and civilians packing a wintry Pyongyang square, ceremonial head of state Kim Yong-Nam praised the late leader for contributing to "global peace and stability of the 21st century.”

Tens of thousands of weeping North Koreans bade farewell Wednesday to longtime leader Kim Jong-Il as his young son and successor walked beside his father's coffin through a snowbound Pyongyang.

Kim Jong-Un was at the forefront of the three-hour procession, in what analysts said was an attempt to bolster the image of the untested new leader of the impoverished but nuclear-armed nation.

North Korea was Tuesday preparing a massive ceremonial farewell to late leader Kim Jong-Il as it strove to strengthen a new personality cult around his youthful son and successor Jong-Un.

The secretive state has so far given no details of Wednesday's funeral for its "Dear Leader" of the past 17 years and has not invited foreign delegations to the ceremony.

South Korea's spy chief has come under fire for questioning North Korea's account of leader Kim Jong-Il's death, as well as failing to learn about his demise before it was officially announced.

The North said Monday that the 69-year-old Kim had died of a heart attack two days previously while on a train during one of his "field guidance" tours, portraying him as a martyr to duty despite the bitter cold.

North Korea's new leader Kim Jong-Un issued his first military order just before his father's death was announced, suggesting the son already controls the armed forces, a report said Wednesday.

Jong-Un ordered all units to halt field exercises and training and return to their bases, Yonhap news agency quoted a senior Seoul government source as saying.

The body of North Korea's long-time ruler Kim Jong Il was laid out in a glass coffin Tuesday as weeping mourners filled public plazas and state media fed a budding personality cult around his third son, hailing him as "born of heaven."

North Korea's official television showed still photos of Kim in the coffin surrounded by wreaths, his body covered with a red blanket and his head on a white pillow. A giant red curtain covered a wall behind Kim.

Secretary of State Hillary Clinton said the United States was "deeply concerned" for North Korea's citizens and offered "thoughts and prayers" in the wake of leader Kim Jong-Il's death.

It is in the U.S. hope the new North Korean leadership "will choose to guide their nation onto the path of peace by honoring North Korea’s commitments, improving relations with its neighbors, and respecting the rights of its people," Clinton said in a statement late Monday.

Japan wants to hold a high-level three-way meeting with the United States and South Korea "as early as possible,” Tokyo said Tuesday, as the allies closed ranks following the death of Kim Jong-Il.

South Korea put its military on alert after the North Korean leader's death was announced on Monday and Japan, which has also been the object of Pyongyang's aggression in the past, ramped up its surveillance.