Celtic have said the club are "appalled" after fans were filmed singing abusive chants about murdered soldier Lee Rigby.

The video was filmed in Sunderland, where Celtic were playing a friendly match against the England Championship side last weekend.

In the video, Celtic fans can be seen chanting "f**k Lee Rigby, you won't be f*****g drumming anymore".

Rigby, 25, a drummer and machine-gunner in the Royal Regiment of Fusiliers, was murdered by terrorists near his army barracks in London in May 2013.

Michael Adebolajo and Michael Adebowale were each sentenced to life imprisonment for the murder.

In a statement, Celtic described their disgust at the chants.

The club said: "Clearly everyone at Celtic is appalled by these events. Such behaviour in no way represents Celtic Football Club or our supporters.

"We understand this incident is now subject to an ongoing police inquiry.

"Let us be clear, in the event that any individuals are identified as being responsible, Celtic will take the strongest possible action."

The game, at the Stadium of Light, was marred by a series of violent incidents across the city, with 21 arrests made.