No casualties were reported in Wednesday's incident, the U.S. military said. Mosul, Iraq's third-largest city, had been relatively quiet in the past several months, but the security situation has deteriorated since October.
The continuing attacks by shadowy groups of Iraqi resistance fighters have cast doubt on the ability of the U.S.-led coalition to contain the growing insurgency, and have sparked an exodus from Baghdad of international organizations and diplomats from several Western countries.
Two senior Iraqi officials said Wednesday that thousands of terrorists have entered Iraq to launch deadly attacks against them.
But despite the growing death toll among American military personnel, the U.S.-led coalition must remain in Iraq to help it emerge from decades of dictatorship and rebuild an economy ravaged by sanctions and war, interim Agriculture Minister Abdul Amir al Aboud said.
"Nobody would like an occupation force to be in the country, but we need them to stay there," al Aboud told reporters. "If they leave now, it would be chaos."
In other developments:
Huge explosions thundered through Baghdad Tuesday evening as the insurgents targeted the 2-square-mile "Green Zone," which includes coalition headquarters, the military press center and other key facilities.
Iraqi police said two mortars fell in the zone, but U.S. officials said the headquarters itself, located in one of Saddam Hussein's former palaces, was not damaged. A Pentagon spokesman said three people were wounded but it was unclear if they were military or civilians.
The huge detonations sent coalition staffers running into the hallways. It was the second mortar attack against the Green Zone in as many days.
There has been a dramatic escalation in attacks on U.S. troops in Iraq. On Sunday, guerrillas near Fallujah shot down a U.S. Army Chinook helicopter, killing 16 soldiers and injuring about 20 others.
"We regret that terrorists are using Iraq to settle scores with the U.S.," Naseer al Chaderchi, a member of Iraq's interim Governing Council and the Sunni National Democratic Party, told reporters through an interpreter at a briefing organized by Australia's foreign ministry.
"Thousands of terrorists came to Iraq and they are doing these acts," he said.
Bush administration officials had hoped a U.N. Security Council resolution approved last month would persuade reluctant allies to send more forces to help in Iraq. No additional countries have contributed forces since.
Turkey had been the most likely. But Turkey's ambassador to the United States, Osman Faruk Logoglu, said his country will not send troops without an explicit invitation from the U.S.-appointed Iraqi Governing Council, some of whose members, particularly Iraqi Kurds, vigorously oppose the idea.
The ambassador said it was up to the Americans to press the Iraqis to make the invitation, which he said the United States appears unwilling to do.
"We felt that the (U.S.) Coalition Provisional Authority and also officials here in Washington could have probably persuaded the Iraqi Governing Council earlier on this issue," Logoglu said.
L. Paul Bremer, the U.S. diplomat who heads the American authority in Iraq, said Saturday that the issue of Turkish peacekeepers was solely between Turkey and the Iraqi Governing Council.
State Department deputy spokesman Adam Ereli said Tuesday the United States still believes Turkish troops would make a valuable contribution, and U.S. officials continue talks on the issue.
Defense Secretary Donald H. Rumsfeld has said more international forces would help ease the burden on the 132,000 American troops in Iraq. Now, about 23,000 other troops from more than 30 countries are there.
Pentagon officials say an infusion of thousands more international troops could prompt a reduction in the number of U.S. forces, although Rumsfeld said last month that any Turkish troops probably would not be in place soon enough to affect the Pentagon's current troop rotation plans.
Under those plans, about 15,000 Army National Guard troops have been mobilized for possible service in Iraq beginning early next year, to replace weary active-duty troops who already have been there close to a year.
Besides the reluctance to send more troops, foreign countries are growing more anxious about having diplomats in Iraq. Spain, a close U.S. ally, withdrew many of its diplomatic staff on Wednesday because of escalating violence. Last month, Bulgaria and the Netherlands moved their diplomats to Jordan, also citing worsening security.