Middlesbrough have signed Barry Robson, Chris Killen and Willo Flood from Celtic, the Championship club have announced.

The trio join former boss Gordon Strachan, who has strengthened his under-performing Boro side.

A statement on the Boro website read: ''Scotland international Robson makes the move to the Riverside for an undisclosed fee, while Flood and Killen both join on free transfers.

''Midfielder Robson has signed a two-and-a-half year contract through to June 2012 with an option for a further year, Flood's contract runs until June 2011 and Killen's until June 2010. All three players, who previously played for Boro manager Gordon Strachan at Celtic, have passed medicals.''