The deployment of the fighter jets is the first since Parliament authorized airstrikes by British forces on Friday against ISIS in Iraq, but not Syria.
Royal Air Force Tornadoes were sent from the Akrotiri air base in Cyprus to Iraq, according to the defense ministry. Photographs released by the ministry appeared to show two aircraft.
The ministry said the planes were "continuing a pattern of flights over Iraq which began in support of the humanitarian mission last month."
It's not yet clear what mission the aircraft are on Saturday or whether they will deploy weapons. But the images appeared to show that they were armed.
Parliament approved military intervention in Iraq after it was recalled for an emergency session Friday.