Colonel Muhammad Abid said on Saturday from his hospital bed that a fellow police colonel and another officer were killed in the ambush which left Abid and two others wounded.
"They blocked our way, shot us and took our cars," he said of the attack in al-Sharqat, 110km north of Tikrit.
Also, a police brigadier and a colonel were shot dead by fighters in the south of Baghdad, police sources said. Both of them worked at the interior ministry. No further details were available.
Elsewhere, a US soldier was killed in al-Anbar province late on Saturday.
Also on Saturday, four employees of the ministry of education were wounded when the bus taking them to work in Baghdad was raked by gunfire.
A woman who survived the attack said in hospital: "We were on our way to work. We go the same way every day. We don't know where the shooting came from."
The four employees worked for
the ministry of education
Two men and two women were wounded.
The yellow, unmarked city bus was riddled with bullet holes in the front and sides. Pools of blood lay inside.
Security officials and civil servants have become prime targets for fighters opposed to the US military and to Iraqis working for the US-backed government.
Also on Saturday a car bomb exploded alongside a US military convoy in the northern city of Mosul, wounding no American forces, the military said. One Iraqi civilian was killed, according to witnesses.
US military spokesman Lieutenant-Colonel Paul Hastings said the blast occurred in eastern Mosul at 10.00am (0700 GMT) as a convoy of Humvees was patrolling the area.
A police official said the attack happened in Mosul's eastern Baath suburb, 360km northwest of Baghdad.
In a separate development, the US military said fighters used a hospital in the volatile city of Ramadi to ambush US soldiers, firing rocket-propelled grenades and small arms fire at troops. In the attack an Iraqi civilian was killed, but there were no American casualties reported.
However, officials from both the Ramadi General Hospital and Medical College rejected the claims, saying fighting occurred near the hospital on Friday night.
The city of Ramadi is a
stronghold of anti-US opposition
Captain Bradley Gordon, spokesman for the 1st Marine Division of the 1st Marine Expeditionary Force, said the firing happened late on Friday as US soldiers attached to the marines were patrolling in Ramadi, 113km west of Baghdad.
Fighters hid inside the Ramadi General Hospital and Medical College and in nearby areas waiting for the soldiers to move into their ambush zone, Gordon said.
"Some of the muzzle flashes of insurgent firing positions were observed as originating from windows within the hospital."
Gordon said US forces fought through the ambush, sustaining no casualties. Hospital official Dr Alaa al-Ani said one Iraqi civilian who was in the vicinity of the clashes was killed by gunfire, but it was not immediately clear who shot him.
Asaad Ali, a hospital official who worked the nightshift when the clashes occurred, rejected the US claims that fighters used the hospital to ambush American troops.
"No armed men entered the hospital yesterday and the hospital was not used to attack anybody," he said. "There were clashes but they took place near the hospital."
Salah al-Ani, dean of the Ramadi Medical College, also denied the military reports, saying he was surprised by such news.
"No armed men entered the hospital yesterday and the hospital was not used to attack anybody"
Ramadi hospital official
Marines will return to the hospital to question administrators about the alleged use of their facilities by fighters for the ambush, the military said. Hospital officials were not immediately available for comment.
Planes raid Falluja
Separately, Iraqi police detained 30 people after a police station north of Baghdad was attacked by mortar and rocket-propelled grenade fire, the US military said.
US forces also arrested a suspected roadside bomb-maker early on Saturday near Baiji, 250km north of Baghdad, according to a statement released by the Tikrit-based 1st Infantry Division.
The detainee was also suspected of aiding non-Iraqi foreign fighters in the area.
Also, US warplanes raided different parts of Falluja including al-Askary, al-Sinai and al-Shuhada neighbourhoods. The raid came after fierce clashes with fighters overnight.
Meanwhile, hundreds of displaced Falluja residents staged a demonstration in Saqlawiya city, northwest of Falluja, demanding to be allowed to return to their city. The demonstrators said that they lived under harsh conditions.