Riyadh - Saudi Arabia, Egypt, Bahrain and the United Arab Emirates announced on Monday they were severing diplomatic ties with Qatar, as tensions escalate in the region over accusations Doha sponsors terrorism.
Saudi news agency SPA said Riyadh cut diplomatic ties and closed borders with its neighbour to "protect its national security from the dangers of terrorism and extremism".
A Saudi official cited by SPA said the country decided to "sever diplomatic and consular ties with Qatar, and to close all land, sea and aviation ports".
The "decisive" measure was due to "gross violations committed by authorities in Qatar over the past years", the Saudi statement said.
The UAE followed suit in cutting ties, and Egypt's foreign ministry also accused Doha of supporting "terrorism" as it announced the severing of diplomatic relations.
The statement said all Egyptian ports and airports would be closed to Qatari vessels and planes.
Bahrain's news agency said the tiny kingdom was cutting ties with Doha over its insistence on "shaking the security and stability of Bahrain and meddling in its affairs".
The Saudi-led Arab coalition fighting rebels in Yemen's two-year war meanwhile said it was expelling Qatar over what it said was the country's support for organisations including Al-Qaeda and the Islamic State group.
Doha has long faced accusations that it is a state sponsor of terror.
It has been criticised in some quarters for its support of rebel groups fighting Syrian President Bashar al-Assad, and Qatari individuals have also been sanctioned by the US Treasury for terror-funding activities.
In recent weeks, Qatar has been accused outright of terror funding in articles which have appeared in the American media.
It was also criticised for providing a sanctuary to former Hamas chief Khaled Meshaal, who earlier this month used his Doha base -- where he has lived in exile for several years -- to launch a new policy document.
The Afghan Taliban opened an office in Doha in 2013.
Qatar, which will host the 2022 football World Cup, is a member of the US-led coalition to defeat the Islamic State group.
The country is also home to the Al-Udeid airbase, where the US conducts all coalition air operations for the region.
Doha 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 last month.
The stories quoted him questioning US hostility towards Iran, speaking of "tensions" between Doha and Washington, commenting on Hamas and speculating that Trump might not remain in power for long.
The alleged comments were made after US President Donald Trump's visit to the region.
However, Doha has denied all the comments and said it had been the victim of a "shameful cybercrime".
Trump's visit to Riyadh - the first foreign stop of his young presidency - saw the two sides sign a "strategic vision" agreement to intensify ties in defence, economics and other areas.
Riyadh has embraced Trump's harder line against its rival Iran, with which it severed diplomatic relations in January last year.
In a Riyadh speech to Muslim leaders from around the world, Trump urged them to "drive out" extremists and "terrorists", as Sunni jihadists carry out attacks in many countries.
But he also singled out Shiite Iran for allegedly fuelling "the fires of sectarian conflict and terror".
Qatar said it had also been the victim of a hostile media campaign, particularly in the US over the issue of its supposed support for Islamist groups.
Qatar has so far given no indication of where the alleged cyber May 24 cyber attack originated.
But regional powers including Saudi Arabia and the United Arab Emirates used the comments to demonstrate that Qatar is out of line with Gulf foreign policy, especially regarding Iran.
Media organisations in several countries in the region reported the emir's comments as fact, despite an official denial by Qatar.
They also blocked Qatari broadcasters and websites following the alleged comments.
In a sign that the rift in Qatar's relations with its near neighbours was deepening, one Saudi newspaper reported that members of a prominent Saudi family had demanded that Qatar's state mosque, the Sheikh Muhammad Ibn Abdul Wahhab Mosque, be renamed.
The demand came amid questions over the Qatari royal family's link to Abdul Wahhab, co-founder of the Saudi state.
Some experts had feared the current situation could trigger a repeat of the crisis in 2014, when several Gulf countries recalled their ambassadors from Doha, ostensibly over its support for the Muslim Brotherhood.
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.