China has formally invited Kim Jong-un, the youngest son of North Korea's leader Kim Jong-il and his likely heir, to visit, South Korean sources say.
The information was relayed to South Korean lawmakers in a security agency briefing and has not been confirmed by Beijing.
No timetable was known for the visit, the security sources said.
The agency also said the North was tightening security amid ongoing unrest in the Middle East.
http://www.bbc.co.uk/news/world-asia-pacific-12655103
Note: 5 March 2011 Last updated at 03:36 GMT