The announcement of Abu Qaswarah's death was withheld until Wednesday to allow for positive identification, the military said.
American officials described Abu Qaswarah, also known as Abu Sara, as a charismatic figure who had rallied al-Qaida's network in the north after the movement suffered major setbacks in Baghdad and other former strongholds.
The Swedish news agency TT reported that the man was also a Swedish citizen. Swedish officials confirmed that a Moroccan Swede suspected of al-Qaida ties was killed in early October and that he was on the U.N. and the EU terror watch lists. They declined to elaborate and it was unclear whether the Swede may have been among the four others killed.
On Oct. 5, the U.S. military reported that 11 people including women and children died in Mosul when an extremist detonated a suicide vest but it was unclear if this was the same incident in which Abu Qaswarah died.
The death of such a senior al-Qaida leader will cause a major disruption to the terror network, particularly in northern Iraq, where the movement remains active, the military said.
"It's going to be much more difficult for the factions left in that area to network and operate among themselves," U.S. spokesman Brig. Gen. David Perkins said. "It allows the Iraqi security forces with the support of the coalition to go in and continue to tear apart that network."
U.S. military officials said Abu Qaswarah, whose real name was unavailable, was a key figure in the al-Qaida network with ties to the movement's global leadership in Pakistan and Afghanistan, where he trained.
That suggested that many of al-Qaida in Iraq's key leaders have remained in the country despite recent reports that many foreign fighters had fled to Afghanistan and Pakistan, where fighting has been on the rise.
A U.S. statement said Abu Qaswarah became the movement's emir, or chief, for northern Iraq in June 2007 and served as second-in-command of al-Qaida in Iraq behind the group's shadowy national leader Abu Ayyub al-Masri, also known as Abu Hamza al-Muhajir.
During a news conference, Rear Adm. Patrick Driscoll, another U.S. spokesman, said Abu Qaswarah supervised the smuggling of foreign fighters into northern Iraq and reportedly killed those who tried to return home rather than carry out suicide bombings and other attacks against Iraqis.
"His death will significantly degrade AQI operations in Mosul and northern Iraq, leaving the network without a leader to oversee and coordinate its operations in the region," the U.S. statement said.
It was unclear what effect Abu Qaswarah's death would have on al-Qaida operations in Mosul.
Senior American military officers have said al-Qaida in Iraq has proven more resilient than other insurgent groups because of its ability to successfully replace its leaders who are killed or captured.
Nevertheless, the death of al-Qaida in Iraq's founder, Abu Musab al-Zarqawi, is widely seen as a major setback because it cost the movement its most energetic and galvanizing figure. He was killed in a U.S. airstrike in June 2006 in Diyala province.
Nationwide, violence has declined drastically over the past year, particularly in Baghdad, but the U.S. military has consistently warned that al-Qaida in Iraq and other insurgents remain a serious threat -- especially in the north.
A recent series of killings of Iraqi Christians in Mosul, widely blamed on al-Qaida, has highlighted the ongoing dangers in the north, where many Sunni insurgents fled intensive U.S. military operations in the capital and surrounding areas.
The number of Christian families escaping violence in Mosul since last week has reached 1,390 -- more than 8,300 people -- local migration official Jawdat Ismaeel said Wednesday.
Ismaeel said humanitarian teams are distributing food and aid materials to all displaced families, who are largely seeking refuge in nearby Christian-dominated towns and villages.
Islamic extremists have frequently targeted Christians and other religious minorities since the 2003 U.S.-led invasion, forcing tens of thousands to flee Iraq. However, attacks declined as areas became more secure after a U.S. troops buildup, a U.S.-funded Sunni revolt against al-Qaida and a Shiite militia cease-fire.
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