LONDON (AP) — The wife of a British aid worker held hostage by the Islamic State group has issued a statement pleading for the militants to release him.

Former taxi driver Alan Henning was kidnapped in December in Syria, shortly after crossing into the country from Turkey in an aid convoy. His wife, Barbara, said he was driving an ambulance loaded with food and water at the time.

The Islamic State group, which has released online videos showing the beheading of two American journalists and another British aid worker, has threatened to kill 47-year-old Henning next.

In a statement released by the Foreign Office, Henning's wife called on "the people of the Islamic State to see it in their hearts to release my husband," and described him as a "peaceful, selfless man."