Iraqi officials say two Iraqi policemen and two civilians have been mistakenly killed by U.S. troops after a U.S. convoy was bombed south of Baghdad.

U.S. military officials have not commented on the incident, which the Iraqi Interior Ministry said occurred late Saturday in an area known as the triangle of death.

In a separate incident, U.S. authorities have expressed deep regret for the mistaken bombing Saturday of a house near the northern city of Mosul. U.S. officials say five people were killed when U.S. airstrikes hit the wrong house. Witnesses and journalists say 14 were killed. U.S. officials say a probe is continuing.

Meanwhile, authorities say seven Ukrainians and a Kazakh soldier were killed Sunday while trying to detonate an ammunition cache southwest of the capital, in Wasit province.

Elsewhere, police in Samarra say assassins have gunned down the city's deputy police chief in a drive-by shooting.