Unidentified bombers have reportedly launched an air strike on ISIS positions in the northern Iraqi city of al-Qaim. Iraqi television has claimed they are US planes, but the Pentagon has denied responsibility.

US planes were identified by Iraqi television, but the Saudi Al-Arabiya network claims that the raid was carried out by Syria, citing local tribal chiefs.

ABC News cited a US official as saying that the Syrian air force is thought to have launched the air strike. The US has “pretty good information that the Syrians are behind the fighter aircraft bombing in western Al Anbar,” the official said.

The Turkish Anadolu Agency has claimed that 20 people have died, and 25 more were injured in the raid, which allegedly targeted the local market.

The radical Sunni Islamic State in Iraq and the Levant (ISIS) has taken large parts of the north of the country from the Shia government, pushing Prime Minister Nouri Maliki to request support from the United States and neighboring Shia states.

Syria’s President Bashar Assad is an Alawite, following a branch of Shia teachings.

Despite Maliki’s plea for air strikes last week, the White House has made no commitment beyond saying that they are “an option.” It has, however, dispatched 300 'military advisors' to help the government.

Iraq’s own air force has been carrying out attacks from on insurgent strongholds over the past week.