SEOUL- Pyongyang has maintained a stony silence over the deportation from Japan of a man believed to be the son of North Korean supreme leader Kim Jong-il.

Intelligence sources in the South Korean capital forecast the secretive North would remain mum for good over the bizarre episode involving the man who reportedly identified himself to Japanese authorities as Kim Jong-il’s eldest son, Kim Jong-nam.

"The silence will be kept for ever," said a South Korean intelligence officer. "The North will not even consider issuing any denial statement on what is perplexing its leadership in Pyongyang."

He added it was strictly taboo to make public comments on the "royal family of Kim" in the tightly-controlled North.

The junior Kim, believed to be 29, disappeared from media view suddenly when he arrived in China May 4 after being deported from Japan.

He was detained at Tokyo’s Narita airport last May 1 along with three companions, presumed to be his wife, four-year-old son and a female relative, for using a fake Dominican Republic passport.

He is reported to have told officials he wanted to take the family to Tokyo Disneyland.