Six mortar bombs have landed near a border post in northern Saudi Arabia in an attack claimed by an Iranian-backed Iraqi Shia armed group, which said it was warning the kingdom to stop meddling in Iraqi affairs.

The mortar rounds hit desert on the far northwestern fringes of the kingdom's oil-producing region on Wednesday, several hundred kilometres from the major fields operated by the world's largest oil exporter and biggest Arab economy.

"The goal was to send a warning message to Saudis to tell them that their border stations and patrol are within our range of fire," Wathiq al-Batat, commander of Iraq's al-Mukhtar Army group, told the Reuters news agency on Thursday.

He said the group wanted Riyadh to stop "interfering" in Iraq and that it had also been angered by Saudis and Kuwaitis who he said had insulted the Prophet Mohammad's daughter.

There was no independent confirmation that the armed group was behind the mortar fire, reported two days after twin suicide bombings killed 25 people near Iran's embassy in Beirut. A Lebanon-based Sunni group linked to al-Qaeda has claimed responsibility for the attack.

Some Shia commentators blamed that assault on Iran's regional rival Saudi Arabia, which has condemned the Beirut attack.

'No high alert'

Saudi Interior Ministry spokesman Major-General Mansour Turki said Iraq and Kuwait, as well as the kingdom itself, were investigating the mortars that landed in the Kingdom.

Iran has not commented on the mortar attack. Baghdad said it was not involved.

"There were no rockets or anything fired towards the Saudi border by security forces," said Jabar al-Sa'adi, head of Basra provincial council's security committee, in southern Iraq.

Turki said Saudi forces had not been put on higher alert after the bombardment.

Saudi news website sabq.org published pictures of small craters in the desert which it said the mortar fire had caused.

A high barbed-wire fence and a road were visible in some photos.

"Six mortar rounds fell in an uninhabited area near the new al-Auja border guard centre of Hafr al-Batin in Eastern Province. Thank God, no damage resulted," said border guard spokesman General Mohammed al-Ghamdi.

Al-Mukhtar Army is a relatively new Shia armed goup, which has said it is supported and funded by Iran. Batat is a former leader of the more well-known Kata'ib Hezbollah armed group.

Sunni Muslim Saudi Arabia, a close ally of Kuwait, has had tense relations with the Shia-led Iraqi government, which it views as a pawn of Iran.