Six US and four British soldiers have been killed in separate attacks in Iraq, while a US helicopter also crashed south of Baghdad.
Four British soldiers and an Iraqi interpreter were killed by a roadside bomb in Iraq.
A fifth soldier was seriously wounded in the blast in the southern city of Basra.
Referring to the deaths, British Prime Minister Tony Blair blamed what he described as elements in the Iranian regime for financing and arming terrorism in Iraq.
The British force had been attacked by roadside bombs, rocket-propelled grenades and small arms fire on the western outskirts of Basra as it returned from an operation.
This has been one of the deadliest weeks for British forces since the invasion in 2003.
In Baghdad, the US military also announced more casualties, saying six soldiers had been killed over the past two days.
Four soldiers were killed on Wednesday by roadside bombs in southern Baghdad and north of the capital, and two more were shot dead by insurgents in eastern parts of the capital on Tuesday and Wednesday.
And four personnel on board a US army helicopter were wounded when it crashed south of Baghdad.
Five others on board were safe, but the US military did not specify the circumstances in which the helicopter crashed.
Earlier reports said a Black Hawk crashed after being hit by ground fire in the Sunni stronghold town of Latifiyah, 40km south of Baghdad.
