Six Iraqi policemen were killed and 10 others wounded when unidentified fighters fired mortars at an Iraqi police checkpoint near Buhriz, a Sunni Arab stronghold 55km northeast of Baghdad.
The fighters then stormed the position firing from eight vehicles, police said on Friday.
Five Interior Ministry commandos were also killed when a roadside bomb exploded near their convoy in Tuz Khormato, 210km north of Baghdad, police Brigadier-General Sarhad Qadir said.
Four other commandos were also wounded.
Meanwhile, a US soldier from Task Force Baghdad was fatally injured when a roadside bomb exploded near his convoy in east Baghdad, the military said.
Another US serviceman died on Thursday near Talil, 270km southeast of Baghdad, apparently of non-hostile causes, a US military statement said.
The latest deaths brought to 2042 the number of US military service members who have died since the war began in 2003, according to the Pentagon.
Elsewhere, a mortar round that missed a US base on the western outskirts of Baghdad struck a home, killing a child and wounding the mother and another one of her children, police Lieutenant Ahmed Ali said.
Two mortar shells exploded after sundown near the edge of Baghdad's Green Zone, which contains key Iraqi government offices and international missions. There were no casualties, police said.
Civilians were killed and wounded
when a mortar shell hit their home
Unidentified armed men also shot and killed Tarik Hasan, a former colonel in the Iraqi air force, as he drove through Baghdad on Thursday, said police Captain Talib Thamir.
Rumor has spread through Baghdad that Shia "hit squads" are hunting former air force officers, especially those who fought against Shia-led Iran during the 1980-1988 war.
Also Friday, the US military announced that it had killed five senior al-Qaida figures during an air strike on 29 October against three buildings in Husaybah, a town near the Syrian border.
The US military says the town sits astride a major infiltration route for foreign fighters and would-be bombers entering the country.
The five included at least one North African and were holding a strategy meeting in one of the buildings when the air strike occurred, the US statement added.
Eid al-Fitr celebrations
On Friday,the Shia community began celebrating the Eid al-Fitr holiday which marks the end of the holy month of Ramadan.
Sunnis began the three-day holiday on Thursday.
Despite the security crisis, some families turned out in parks around the city, putting aside their fears to celebrate the Eid holiday. In the Shia district Sadr City, crowds of children lined up for rides at small local amusement parks.
Security by police and local militias remained tight to protect holidaymakers from car bombs, drive-by shootings and roadside bombs.
"We cannot fully enjoy Eid because of all the explosions we hear," said Karar al-Aboudi, 25, the owner of a stall near one park.
"We have no reason to celebrate under occupation and terrorism. We pray to God that in the next Eid, our country will be stable and free."
In related news, a statement from the al-Qaida in Iraq group has warned foreign diplomats of repercussions and demanded they leave Iraq.
"We are renewing our threat to those so-called diplomatic missions who have insisted on staying in Baghdad and have not yet realized the repercussions of such a challenge to the will of the mujahedin," the Friday statement said.
Al-Qaida in Iraq said it would
execute the Moroccan envoys
"Let them know that there is no difference in our judgment between the head of a diplomatic mission and the lowest-level employee."
The statement came after an earlier announcement that the group will put to death two kidnapped Moroccan Embassy employees.
The two Moroccans, driver Abderrahim Boualam and embassy staff member Abdelkrim el-Mouhafidi, disappeared Oct. 20 while driving to Baghdad from Jordan, where they had gone to pick up their paychecks.
The warning came in a statement posted on an Islamist Web site in the name of al-Qaida in Iraq, which also claimed responsibility for the July kidnap-slaying of two envoys from Algeria and one from Egypt as well as the abduction and beheading of many foreign hostages.
The al-Qaida threat appeared aimed at undermining support for the US-backed Iraqi government within the Arab and Islamic worlds.
In addition to the Egyptian and Algerian diplomats, senior envoys from Pakistan and Bahrain escaped kidnap attempts in July.