North Korea's official Korean Central News Agency reported Monday that leader Kim Jong Il is dead at the age of 69, and will be succeeded by the youngest of his three sons, Kim Jong Un.

The agency said the leader died after an "advanced acute myocardial infarction" -- i.e., a heart attack -- during a train ride at about 8:30 a.m. on December 17.

"He passed away too suddenly to our profound regret," a statement from the agency reads. "The heart of Kim Jong Il stopped beating, but his noble and august name and benevolent image will always be remembered by our army and people."