A 16-year-old grandson of North Korean leader Kim Jong-Il has reportedly been denied a visa to study in Hong Kong, despite being described by his prospective school as a "lovely kid" with a "good sense of idealism".

Kim Han-Sol was accepted by an international school run by the United World Colleges (UWC) network but his visa bid was turned down despite several requests, the former school principal was quoted as saying.

Hong Kong's immigration department Thursday declined to confirm whether the teenager had applied for a visa, saying it did "not comment on individual cases", but suggested such a decision would be in line with general policy.

The department said people from countries including North Korea, Nepal and Cambodia were barred from obtaining a student visa -- although exceptions are given in certain cases based on merit.

"The government will take into account factors which include immigration and securities considerations, economic, social and cultural ties between Hong Kong and the country," it said.

Former school principal Stephen Codrington, who interviewed Kim Han-Sol, described him as a "lovely kid, very bright, charismatic" with "good English" and a "good sense of idealism", the South China Morning Post reported.

The 16-year-old's father is Kim Jong-Nam, the North Korean leader's exiled eldest son, according to the Post. The pair are said to have lived in Macau -- an hour's ferry ride from Hong Kong -- since the father fell out of favour with Kim Jung-Il years ago.

Kim Jong-Nam is understood to have once been the frontrunner to succeed the North Korean leader. But youngest son Kim Jong-Un is now being groomed to take over one of the world's most isolated countries.

Following the visa denial in Hong Kong, Kim Han-Sol was enrolled at another UWC school -- in the southern Bosnian town of Mostar. A school spokeswoman told AFP last Friday he was still waiting for a Bosnian visa and was yet to arrive.

The Bosnian school said the enrollment was the result of the UWC's special outreach programme for North Korea.

The UWC is a worldwide network of schools and colleges, which promotes international understanding and is attended notably by pupils from war-affected areas.