Saracens held onto top spot in Pool Five of the European Challenge Cup with a hard-earned 16-6 victory over Bayonne at Stade Jean Dauger.

Replacement Mosese Rauluni settled a tight encounter with the game's only try four minutes from time.

Rauluni picked up from the base of a scrum and scurried over for an opportunist try after Kevin Sorrell had seen his effort ruled out.

Tempers had flared amid the stalemate when props Census Johnston and Julian Fiorini were sin binned for punching early in the second half.

Daniel Larrechea levelled the scores but Jackson held his nerve to nudge Saracens ahead before Rauluni's late score.