One US soldier has been killed and seven wounded in a roadside bombing near the key northern Iraqi oil refinery town of Baiji, the US military said.

One Task Force Danger soldier was killed and seven wounded in an improvised explosive device attack on a US combat patrol near Baiji, 200km north of Baghdad, said a statement on Friday.

No further details were immediately available.

The latest figures bring to 1446 the number of US soldiers killed since the US invasion in March 2003.

Meanwhile, a purported Iraqi group - the Army of Ansar al-Sunna - said on Friday it had killed 29 Iraqis and taken seven prisoners when it ambushed a 50-strong Iraqi police convoy this week, an internet statement said.

"The lions of God yesterday set a trap for a National Guard convoy at Abu Ghraib west of Baghdad ... after a fierce battle the mujahidin killed 29 people, burned four trucks soldiers were riding in, and took seven prisoners," the group said in a statement dated Friday, posted on its website.

Iraqi forces intimidated

In related news, the intimidation of Iraqi soldiers by anti-US forces has hampered efforts to build a reliable security force, the US general in charge of training Iraqi troops said on Friday.

Army Lieutenant-General David Petraeus, speaking from Baghdad to reporters at the Pentagon, said the Iraqi units had suffered "losses due to severe intimidation", but he offered no specifics. He did not cite an absentee or desertion rate.

By next week, when 3500 replacements become available for duty, the 90 battalions of police, army and other types of security forces will be at 80% of their intended manpower levels, Petraeus said.

Referring to the overall state of training, Petraeus said "considerable momentum has been achieved" towards reaching the point where Iraqi forces can take the lead role. He said Iraqis already are taking the lead in 12 of the country's 18 provinces.

PHOTO CAPTION

U.S. marines line up Wednesday during a memorial service for 31 U.S. servicemen who were killed last week when their helicopter crashed near Ar Rutbah, western Iraq. (AP)