Riyadh (AFP) - Arab nations including Saudi Arabia and Egypt on Monday cut ties with Qatar accusing it of supporting extremism, in the biggest diplomatic crisis to hit the region in years.
Bahrain, the United Arab Emirates and Yemen joined Saudi Arabia and Egypt in severing relations with gas-rich Qatar, with Riyadh accusing Doha of supporting groups, including some backed by Iran, "that aim to destabilise the region".
Qatar reacted with fury, denying any support for extremists and accusing its Gulf neighbours of seeking to put the country under "guardianship".
The crisis was likely to have wide-ranging consequences, not just for Qatar and its citizens but around the Middle East and for Western interests.
Qatar hosts the largest US airbase in the region, which is crucial to operations against Islamic State group jihadists, and is set to host the 2022 football World Cup.
Monday's announcement came less than a month after US President Donald Trump visited Saudi Arabia to cement ties with Riyadh and called for a united front among Muslim countries against extremism.
It also followed weeks of rising tensions between Doha and its neighbours, including Qatari accusations of a concerted media campaign against the country and the alleged hacking of the Qatar News Agency.
Qatar slams 'baseless claims'
The Gulf states and Egypt said they were severing diplomatic ties and closing transport links with Qatar, which relies heavily on imports from its neighbours.
The Gulf states banned their citizens from travelling to Qatar and ordered Qatari citizens to leave within 14 days.
Saudi Arabia also closed its borders with Qatar, effectively blocking food and other supplies exported by land to Qatar.
Local media in Qatar reported there was already some panic buying by people stocking up on food.
Riyadh said in a statement the moves aimed to "protect its national security from the dangers of terrorism and extremism".
The measures were the result of "gross violations committed by authorities in Qatar," Riyadh said, accusing Doha of harbouring "terrorist and sectarian groups that aim to destabilise the region including the Muslim Brotherhood, Daesh (IS) and Al-Qaeda".
Gulf states have for years accused Qatar of supporting extremist groups, in particular the Muslim Brotherhood, the world's oldest Islamist organisation.
Riyadh in its statement on Monday also accused Doha of supporting Iran-backed "terrorist activities" in Saudi Arabia's Shiite-dominated area of Qatif, as well as in Bahrain, both of which have seen Shiite unrest over the past six years.
Any suggestion that Qatar is backing the agenda of Shiite-dominated Iran -- Sunni Saudi Arabia's regional arch-rival -- is especially sensitive, particularly in the wake of Trump's comments last month.
Qatar has consistently denied any support for extremists or Iran and did so again after Monday's move by its neighbours.
"The measures are unjustified and are based on false and baseless claims," the Qatari foreign ministry said in a statement.
"The aim is clear, and it is to impose guardianship on the state," it said, insisting authorities would "take all measures necessary... to foil attempts to affect or harm Qatar's society and economy".
The economic consequences were already emerging, with UAE carriers Emirates, Etihad, flydubai and Air Arabia, as well as Saudi Airlines, announcing the suspension of all flights to and from Qatar as of Tuesday morning.
Qatar Airways -- one of the region's busiest airlines -- said it had suspended all flights to Saudi Arabia with immediate effect, at least until the end of Monday. It was unclear whether the suspension would be extended.
Yemen's internationally recognised government also announced it was cutting ties with Qatar and a Saudi-led coalition battling Iran-backed rebels in Yemen said it had expelled Doha from the group.
The coalition accused Qatar of providing "support to (terrorist) organisations in Yemen" -- the first time it has made such a claim.
Gulf countries previously recalled their ambassadors from Qatar in 2014, ostensibly over its support for the Muslim Brotherhood, but Monday's moves go much further.
Saudi Arabia and its Gulf allies may have felt emboldened by Trump's visit, which saw the new president clearly align US interests with Riyadh and lash out at Iran.
Speaking in Sydney, US Secretary of State Rex Tillerson said he did not expect the announcement to have "any significant impact, if any impact at all, on the unified fight against terrorism in the region or globally".
He also encouraged Qatar and its neighbours to "sit down together and address these differences".
Doha last month launched a probe into an alleged "hack" of state media after it said false and explosive remarks attributed to Emir Sheikh Tamim bin Hamad Al-Thani were published on the Qatar News Agency website following Trump's regional visit.
The stories quoted him questioning US hostility towards Iran, speaking of "tensions" between Doha and Washington, and speculating that Trump might not remain in power for long.
Doha denied all the comments and said it had been the victim of a "shameful cybercrime".
Qatar has been criticised for supporting rebel groups fighting Syrian President Bashar al-Assad, and Qatari individuals have been sanctioned by the US Treasury for terrorist-funding activities.
In recent weeks, articles in the US press have accused Qatar of such funding, prompting Doha to complain it was the target of a hostile media campaign.
Qatar has so far given no indication of where the alleged May 24 cyber attack originated.
Media organisations in several regional countries reported the emir's comments as fact, despite an official denial by Doha.
They also blocked Qatari broadcasters and websites -- including the influential Doha-based Al-Jazeera news channel -- following the alleged statements.
Last week, the Qatari emir travelled to Kuwait to meet Emir Sheikh Sabah al-Ahmad Al-Sabah in what was widely seen as an attempt at mediation by the Kuwaitis.