The midfielder has been unwell for several days but reported for international duty with South Korea despite missing the Hoops' last two games against Rennes and Motherwell.

Reports today claim he underwent a series of tests after feeling sick and dizzy upon arrival in his homeland.

A club spokesperson told Celtic's website: "It is well known that Ki was unwell for a number of days and, while in Glasgow, we made it our priority to ensure he received the appropriate rest and the usual high quality of care and treatment from the Celtic medical staff.

"Unfortunately, the South Korean FA demanded that he travel and then, as Ki still felt unwell, they decided to carry out various tests.

"We are pleased that these tests have returned normal results.

"We look forward to Ki's condition improving and to him returning after the international break."