By Pol O Gradaigh

Manama/Riyadh (dpa) - Bahrain, the United Arab Emirates and Sudan followed ally Saudi Arabia's lead in severing or downgrading ties with Iran as regional tensions escalate over the Saudi execution of a Shiite dissident cleric.

Bahrain and Sudan cut off diplomatic links with Iran on Monday, and the UAE downgraded its ties with the Islamic Republic.

Riyadh meanwhile stepped up its own measures against Tehran, with Saudi Arabia's General Civil Aviation Authority announcing that airlines had been instructed to stop all flights to and from Iran.

The diplomatic fallout came only hours after the Saudi government broke off relations with Tehran, where protesters had stormed the Saudi embassy on Saturday night to protest Riyadh's execution of Shiite sheikh Nimr al-Nimr, a fiery critic of the Saudi authorities.

Al-Nimr was among 47 people executed by Saudi Arabia on Saturday after their convictions on terrorism-related charges.

Bahrain and the UAE accused Iran of interfering in the internal affairs of Gulf and Arab countries, and Sudan said it was acting "in solidarity" with Riyadh.

Manama has ordered Iranian diplomats to leave its territory within 48 hours, the official Bahrain News Agency reported.

Bahrain charged Iran with "blatant and dangerous interference" in the internal affairs of Arab countries and support for terrorism.

The island state, whose Sunni ruling family is closely allied to Saudi Arabia, has seen two days of protests by members of its Shiite majority since al-Nimr's execution.

The UAE meanwhile pulled its ambassador from Tehran and said it was downgrading links to the level of charge d'affaire.

The country would also cut the number of Iranian diplomats on its soil, its Foreign Ministry said.

The oil- and gas-rich Arab Gulf states have long suspected Iran of seeking regional dominance and inciting unrest among Shiite populations in Bahrain and Saudi Arabia.

The Sudanese Foreign Ministry said Khartoum was cutting off relations with Iran "in solidarity with the sister kingdom of Saudi Arabia in confronting the Iranian plans."

Sudan previously had close relations with Tehran, but has increasingly been leaning towards Saudi Arabia.

In recent months it has sent hundreds of troops to support the Saudi-backed government in Yemen against Iran-aligned Houthi rebels.

There have been reports of unrest in the eastern Saudi Arabian governorate of Qatif, al-Nimr's home region and a stronghold of the country's restive Shiite minority.

A civilian was killed and an 8-year-old injured when gunmen opened fire on police in the cleric's hometown of Awwamiyeh, police said Monday.

The incident took place as security forces were trying to recover a stolen vehicle, a police statement said.

Awwamiyeh and neighbouring Qatif city have seen frequent protests in recent years.

Al-Nimr was sentenced to death in 2014 on charges of causing sectarian strife and disobeying the ruler.

The trial was condemned as unfair by human rights groups and his supporters say he had only called for peaceful protests and criticized the ruling Al Saud family.

The execution has provoked a furious reaction from Shiite Muslims in the region. Iran's Supreme Leader Ayatollah Ali Khamenei threatened Saudi Arabia with "divine vengeance" for executing al-Nimr.