Six mortar bombs landed near a border post in northern Saudi Arabia on Wednesday in an attack claimed by an Iranian-backed Iraqi Shia militia, which said on Thursday it was warning the kingdom to stop meddling in Iraqi affairs.
The mortar rounds hit the desert on the far northwestern fringes of the kingdom's oil-producing region, several hundred miles 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 militia, told Reuters in Baghdad by telephone.
He said the militia 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 Muhammad's daughter.
There was no independent confirmation that the militia was behind the mortar fire. Iran has not commented.
The bombs were reported two days after twin suicide bombings killed 25 people near Iran's embassy in Beirut, an attack claimed by a Lebanon-based Sunni group linked to Al-Qaeda.
Some Shia commentators, however, blamed the Beirut bombings on Iran's regional rival Saudi Arabia.
Saudi Arabia, which has condemned the attacks, on Thursday urged its citizens to leave Lebanon, out of fear that sectarian violence is on the rise there. A statement issued by the Saudi Embassy in Beirut called for citizens to "return to the kingdom and be cautious."
Saudi Interior Ministry spokesman Maj. Gen. Mansour Turki said Iraq and Kuwait, as well as the kingdom itself, were investigating the mortar fire. Baghdad said it was not involved.
"There were no rockets or anything fired towards the Saudi border by security forces," said Jabar al-Saadi, head of the security committee for the Basra provincial council in southern Iraq.
Turki said Saudi forces had not been put on higher alert after the bombardment.
The Saudi news website sabq.org published pictures of small craters in the desert that it said the mortar fire had caused. A high barbed-wire fence and a road were visible in some photos.
Al-Mukhtar Army is a relatively new Shia militia, which has said it is supported and funded by Iran. Batat is a former leader of the better-known Kataib Hezbollah militia.
"This is just the beginning, and there will be more attacks if (the Saudis) do not stop," he said.
Mustafa Alani, an Iraqi security analyst with the Geneva- and Jiddah-based Gulf Research Center, said Al-Mukhtar was among several Iraqi groups with ties to Iranian intelligence.
"The timing is linked to the attack on the embassy (in Beirut)," he told Reuters, adding that the group might also have been trying to sabotage a call made this month by Iraqi Prime Minister Nouri al-Maliki for better ties with Saudi Arabia.
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. It has not had an ambassador based in Baghdad since before the 1990-91 Gulf crisis.
Sectarian fighting in Iraq since the U.S.-led invasion in 2003 has involved Sunni militants close to Al-Qaeda as well as Shia militias that have no love for Saudi Arabia.
Some Iraqi Shias support Syrian President Bashar al-Assad in his two-and-a-half-year-old struggle to crush what has become an armed revolt by mainly Sunni rebels, some of them backed — and armed — by Riyadh.
The conflict has aggravated Sunni-Shia antagonism across the region, not least in Syria's smaller neighbor Lebanon, where Iran and Saudi Arabia have long vied for influence.