BAGHDAD, Iraq (CNN) -- A U.S. military commander Friday reported the death of a senior al Qaeda in Iraq leader, a Tunisian who was considered the "emir of foreign terrorists in Iraq."
U.S.-led coalition forces killed militant leader Abu Usama al-Tunisi on Tuesday in Mussayib, south of Baghdad, said Army Brig. Gen. Joseph Anderson, speaking to Pentagon reporters via teleconference from Iraq.
Anderson called the death "a significant blow" to al Qaeda in Iraq -- a Sunni-dominated militant group that takes its inspiration from Osama bin Laden's al Qaeda.
Military commanders have said the leadership in the Iraqi group includes many foreigners, while the rank-and-file members are Iraqis.
Anderson called al-Tunisi "a close associate and part of the inner circle of close advisers to Abu Ayyub al-Masri ... the overall leader of al Qaeda in Iraq and his likely successor."
Al-Tunisi had operated in Yusufiya, southwest of Baghdad, since the second battle of Falluja in November 2004 and became "overall emir" for the region in the summer of 2006, Anderson said.
His group was involved in the kidnapping of American soldiers in 2006, the military commander said.
As "emir for foreign terrorists," al-Tunisi reportedly coordinated the movement of such fighters into the country and helped equip insurgents for bomb attacks.
Meanwhile, a coalition raid Friday left at least 10 people dead in Baghdad -- some of whom may have been noncombatants, an Iraqi Interior Ministry source said.
A coalition account described the dead as insurgents.
The raid by coalition troops, aided by Iraqi special forces, targeted a residential building in southern Baghdad's Dora district, an Interior Ministry source said.
Twelve people also were injured, and apartments were damaged, including some that caught fire, the source said.
The deaths come at a time when the Iraq government has expressed concern over Iraqi civilians caught in crossfire and killed by coalition forces or U.S. contractors.
The U.S. military said Thursday that coalition forces were investigating an incident Tuesday night that led to the deaths of nine civilians -- five women and four children. Their bodies were found in a village west of Musayyib.
In a coalition raid Wednesday, U.S. soldiers discovered insurgent propaganda extolling the September 11, 2001, attacks on the United States, the military said Friday. In a cache in a house south of Baghdad, troops found "a small booklet featuring images of the attacks and a script praising the attacks."
"Our assessment is that these guys were getting ready to launch attacks during the Ramadan celebration," said Lt. Thomas Ceislak, referring to the Muslim holy month.
Troops detained the owner of the house. They also found three blasting caps, a ski mask, a terrorist manual that included directions on building car bombs, two cell phones and a card to activate the cell phones.
Meanwhile, the U.N. refugee agency on Friday expressed "grave concern" over the kidnapping and killing of a humanitarian worker in the southern Iraqi city of Basra.
The 31-year-old Iraqi worked for Intersos -- an Italian group devoted to helping victims of natural disasters and armed conflicts -- in a project funded by the U.N. High Commissioner for Refugees.
He was kidnapped Tuesday by militias, which have a large presence in the predominantly Shiite city. The humanitarian worker's body and that of a friend were found in a morgue, according to his group.
The United Nations is not naming the victim "for the security of surviving relatives."
"Because of the extremely difficult security conditions, humanitarian aid efforts in Iraq depend heavily on courageous Iraqi citizens like our Intersos colleague. His death is a tragic loss for his family, for his colleagues and for the overall humanitarian aid effort in Iraq," the U.N. refugee agency said.
The United Nations said it appears the killing was an example "of militia retaliation against sectarian minorities in southern Iraq and not deliberate targeting of humanitarian workers."
CNN's Saad Abedine contributed to this report.