Ravel Morrison has returned to parent club West Ham from Cardiff City on compassionate leave.
Brighton boss Sami Hyypia is weighing up a move for former France captain Alou Diarra.
Brazilian Iriney, 32, who has spent time with Real Betis, Celta Vigo and Rayo Vallecano,joins for an undisclosed fee and pens a deal to keep him at the club until 2015.
Ekstrand's move is made permanent after the Swedish defender spent all of last season on loan with the Hornets, making 36 appearances in all competitions. He has signed a three-year deal at Vicarage Road.
Meanwhile, former Watford defender Carl Dickinson has joined Port Vale.