Police were hunting for clues as to whether al-Qaeda was behind the bombing that shocked the country's large expatriate communiy.
The bomber, an Egyptian national, drove into the one-storey theatre near a British school in the capital Doha during a production of Shakespeare's
Twelfth Night on Saturday.
The blast also injured 16, mostly Arabs and Asians.
Qatar served as command center for US-led forces during the invasion of Iraq in 2003.
