Britain's Prince William was "deeply saddened" by news a close friend had been killed by a roadside bomb in Iraq, his office said on Saturday.
Second Lieutenant Joanna Yorke Dyer was one of four British soldiers who died in a Warrior armoured vehicle as they returned from an operation on Thursday in the southern city of Basra.
Dyer, 24, had trained with William, son of heir-to-the-throne Prince Charles and now a second lieutenant in the army. They graduated as officers from Sandhurst military academy on the same day.
"Prince William was deeply saddened to hear the tragic news of Jo Dyer's death," Charles's office said in a statement.
"Jo was a close friend of his at Sandhurst and he is very much thinking of her family and friends right now and they will remain in his thoughts and prayers."
William, 24, cannot serve in a war zone because he is second in line to the throne but his younger brother Harry, 22, is expected to be deployed to Iraq in the next few months with his Blues and Royals regiment.
Six British soldiers have been killed in Iraq in the last week, making it one of the deadliest for British forces since the U.S.-led invasion in 2003.