Iraqi military forces claim to have launched successful air and ground counterattacks today against the new Iranian offensive in the rugged mountains of northeastern Iraq, but Iran claimed to have repulsed the counterthrust.

A military communique issued here this evening indicated that heavy fighting was continuing.

Iraqi jets and helicopter gunships carried out 273 combat missions in the Haj Omran area, the focus of the Iranian attack, and inside Iranian territory, spokesmen here said. They said Iraqi aircraft were in "full control of the skies" and sustained no losses.

The spokesman said Iraqi forces had killed more than 800 Iranian troops, destroying one armored battalion and six infantry battalions, including two commando units. The statements did not disclose Iraqi casualties.

Iran launched the new offensive in the lightly defended northern sector of Iraq yesterday, claiming to have penetrated 10 miles inside Iraqi territory. Iraqi statements have not responded directly to these claims, and military officials here have not been available for questioning by foreign journalists, who have not been permitted to go to the front.

Official Iranian communiques said Iran had achieved the main objectives of its offensive. Iran said it had captured Haj Omran, which has supplied Kurdish rebels for three years, Reuter reported from Tehran.

The Iranians also claimed to have shot down an Iraqi plane.

Agence France-Presse added that the Iranian foreign minister, Ali Akbar Velayati, warned Sunday that any attempt to paralyze Iranian oil exports would be answered by Iran with blocking of oil exports from other Persian Gulf countries.

Iran said yesterday that the attack had been launched to seize artillery positions used to shell Iranian border villages and to cut a road Iraq uses to supply Kurdish rebels in Iran.

There has been speculation here that the assault may have been intended as a thrust to vital Iraqi oil fields and the pipeline to Turkey, Iraq's only remaining means of shipping out its oil.

Western military analysts here said today, however, that they doubted Iranian forces had the logistical capability to mount a sustained offensive across the extremely difficult northern mountains. They said they expected the Iranian assault to fade in the next few days as Iraq takes full advantage of its strategic positions and air superiority.

The assault was seen by these observers as the latest round in what increasingly appears to be a war of attrition, after nearly three years of fighting. Each side accuses the other now of not aiming for decisive military victory but at wrecking the other economically.

Unknown, however, was what role Kurds were playing in the new battle. While Iran cited the collaboration of Kurds in Iran with Iraqi forces as one reason for its offensive, Iraqi spokesmen have accused Kurds in Iraq of aiding advancing Iranian forces.

Whether this reflects a clever game by the Kurds of playing Iran off against Iraq or reflects divisions among the Kurds was unclear.