Iraq has accused Iranian troops of crossing into its territory and seizing an oil well that lies in a disputed area along the southern border of the two countries.

Iraq's deputy minister Mohammed Haj Mahmoud said 11 soldiers seized oil well No .4 Thursday night in the al-Fakkah oil field, located about 320 kilometres southeast of Baghdad.

Crude prices rose nearly a dollar on Friday to over $73 US after news of the incident.

While the two countries share the oil field, Iraq considers oil well No. 4 their property.

Mahmoud called for the immediate withdrawal of Iranian forces from the area.

A U.S. official said while Iranian forces have crossed into Iraq before, they have not entered this far in recent years. The Iran-Iraq border was never clearly defined in some areas after the brutal war between the two countries in the 1980s.

The U.S. official, speaking on condition of anonymity because he was not authorized to speak on the record, said it is believed the Iranian forces have already left the area. The U.S. military said it did not have any information on the incident.

The National Iranian Oil Company denied Iranian troops crossed into Iraqi territory in a statement to the semi-official Mehr news agency.

With files from The Associated Press