(Adds U.S. says coalition air strike far from site of blast)
BAGHDAD, March 12 (Reuters) - Soldiers from an Iraqi army unit in the western province of Anbar have been killed in what seemed to be a 'friendly fire' incident, an Iraqi military officer and a police source said on Thursday.
The military source said 22 soldiers were killed on Wednesday when an aircraft bombed the headquarters of an army company on the edge of Ramadi city, Anbar's provincial capital.
The source said he believed the bomb was launched from a U.S.-led coalition aircraft, but coalition spokesman Lieutenant Colonel Thomas Gilleran said the only strike it carried out in the province did not result in any "friendly casualties".
U.S. military officials, speaking to Reuters on condition of anonymity, indicated that Iraqi security force aircraft were operating in area where the strike occurred and that U.S. officials are conferring with Iraqi officials about reports of a friendly fire incident among Iraqi forces.
One of the U.S. officials said the coalition air strike in Anbar province on Wednesday was 33 km (21 miles) away from the area where the alleged friendly fire incident occurred.
The Iraq military source said Iraqi aircraft had not operated in the area for two months. "We don't have any Iraqi war planes carrying out combat duties in Anbar," he said.
An Iraqi police source said dozens of soldiers had been killed in what he described as a friendly fire incident, without identifying the nationality of the aircraft which carried out the air strike.
Sabah Karhout, head of the Anbar provincial council, gave an alternative explanation, saying the blast was caused by explosives planted in an underground tunnel beneath the military headquarters.
Iraqi forces have been struggling for more than a year to push back Islamic State militants who control most of the Sunni Muslim Anbar province and swept through northern and central Iraq last June.
The army, backed by militia forces, has launched an offensive to drive Islamic State out of Tikrit, north of Baghdad, but the militants fought back in Anbar on Wednesday, launching at least 13 suicide car bomb attacks on army positions.
The military source said Wednesday's air strike came after officers appealed for aerial support in response to those attacks. (Reporting by Ahmed Rasheed and Saif Hameed in Baghdad, and Phil Stewart in Washington; Writing by Dominic Evans; Editing by Ruth Pitchford)