At least four American soldiers were killed in bomb blasts and a mortar attack, authorities said Friday, bringing the U.S. death toll in Iraq this week to 10 - violence serving as a reminder that resistance fighters remain defiant. Unidentified gunmen also assassinated a tribal leader who backed the coalition near a mosque in the northern town of Mosul. Anti-U.S. fighters have targeted Iraqi police and other officials who cooperate with the U.S.-led occupation authorities. One American GI died Friday as he tried to defuse a homemade bomb in Baqouba, 30 miles north of Baghdad. Capt. Jefferson Wolfe of the Army's 4th Infantry Division said the bomb blew as the soldier worked on it. Such explosives are a favored weapon of Iraqi fighters, who leave them on roadsides and detonate them as military convoys pass. The fighters used that tactic Friday near Balad, north of Baghdad, setting off a bomb that killed a second soldier, a U.S. military spokeswoman said. The U.S. military earlier reported that a third soldier had been killed Friday, but military officials later said the report was wrong and that they had confused the incidents in Baqouba and Balad. The other two deaths came Thursday but were first reported Friday. Two soldiers were killed as Iraqis shelled a U.S. base near Baqouba and four were wounded, Maj. Josslyn Aberle of the 4th Infantry Division said Friday. Also Friday, three soldiers from the U.S. Army's 101st Airborne Division were wounded in an ambush in Mosul when their convoy came under small arms fire, said Maj. Trey Cate, the division spokesman. On Thursday, two Polish soldiers were wounded when attackers hit their convoy with a remote-controlled mine, Col. Zdzislaw Gnatowski told the Polish news agency PAP. The Poles command a multinational force of 9,500 soldiers in south-central Iraq that includes about 2,400 Polish troops. In the Mosul assassination, gunmen in a speeding car shot and killed Sheik Talal al-Khalidi and his 23-year-old son, Saad Talal, said another son, Khalid, who witnessed the attack. A brother of the sheik was injured, and the assailants fled. Al-Khalidi, 57, was a member of the loyalist National Assembly under Saddam who joined a new local governing council that works with U.S. troops. More than 200 people have been arrested since Saddam's capture Dec. 13, many using information in documents seized from Saddam, according to the military. Meanwhile, Japan sent a small advance team Friday to prepare for the deployment of about 1,000 non-combat personnel including more than 500 ground troops in that country's first operation in a conflict zone since World War II. And defense officials in Ukraine said that country's contingent of 1,650 troops in Iraq will be increased by about 150 aviators and six helicopters in early February. **PHOTO CAPTION*** Soldiers of the 402nd Civil Affairs Battalion carry Pfc. Charles Bush Jr. from the services held at the Gethsemane Full Gospel Church in Buffalo, N.Y., Friday, Dec. 26, 2003. (AP Photo/Don Heupel)