A spokesman for British Prime Minister Tony Blair said: "Our thoughts will be with the families of those involved."
The tragedy comes as ground attacks started on Iraq.
British and American forces entered southern Iraq overnight on Thursday.
Regret
Air attacks on the Iraqi capital, Baghdad, also continued overnight.
Ground troops have also been taking control of key oilfields in Iraq.
Tony Blair made an important speech on Thursday night, saying the world would regret it if Saddam Hussein wasn't disarmed and removed from power.
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Iraq war: hour by hour updates
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