Four Arab nations have cut diplomatic ties to Qatar over its relations with Iran and support of Islamist groups, including Hamas, isolating the tiny energy-rich country by cutting off its land, sea and air routes to the outside world.

Bahrain, Egypt, Saudi Arabia and the United Arab Emirates began withdrawing their diplomatic staff from Qatar as regional airlines quickly announced the suspension of services to its capital Doha.

Qatar, which will host the 2022 World Cup and is home to some 10,000 American troops at a major US military base, criticised the move as a “violation of its sovereignty”.

It has long denied supporting militant groups and described the crisis as being fuelled by “absolute fabrications” stemming from the recent hack of its state-run news agency.

However, the crisis immediately wreaked havoc with its long-haul carrier Qatar Airways, sent the Qatari stock market tumbling and raised questions about how a country reliant on food imports would be affected.

The countries all ordered their citizens out of Qatar and gave Qataris abroad 14 days to return home to their peninsular nation. The countries also said they would eject Qatar‘s diplomats from their territories.

Qatar’s Foreign Affairs Ministry said there is “no legitimate justification” for the countries’ decision, though it vowed its citizens would not be affected by it.

“The Qatari government will take all necessary measures to ensure this and to thwart attempts to influence and harm the Qatari society and economy,” it said.

All the nations also said they planned to cut air and sea traffic. Saudi Arabia said it also would shut its land border with Qatar, effectively cutting off the country from the rest of the Arabian Peninsula.

Already, Doha-based satellite news network Al-Jazeera reported trucks carrying food had begun to line up on the Saudi side of the border, apparently stranded. The Qatar Stock Exchange fell more than 7%.

Qatar Airways, one of the region’s major long-haul carriers that routinely flies through Saudi airspace, did not immediately respond to a request for comment. Some of its flights were going through Iranian airspace on Monday.

Premier UAE airlines Etihad and Emirates announced they would suspend flights to Qatar, as did budget carriers Air Arabia and FlyDubai. Bahrain’s Gulf Air and Saudia joined them.

Saudi Arabia also said Qatari troops would be pulled from the ongoing war in Yemen. Yemen’s internationally-backed government, which no longer holds its capital and large portions of the country, also cut relations with Qatar, as did the Maldives.

Qatar is home to the sprawling al-Udeid Air Base, which is home to the forward headquarters of the US military’s Central Command. It was not clear if the decision would affect American military operations.

Saudi Arabia said it took the decision to cut diplomatic ties due to Qatar‘s “embrace of various terrorist and sectarian groups aimed at destabilising the region”, including the Muslim Brotherhood, al-Qaida, Islamic State and groups supported by Iran in the kingdom’s restive Eastern Province.

Egypt’s Foreign Ministry accused Qatar of taking an “antagonist approach” toward Egypt and said “all attempts to stop it from supporting terrorist groups failed”.

The tiny island nation of Bahrain blamed Qatar‘s “media incitement, support for armed terrorist activities and funding linked to Iranian groups to carry out sabotage and spreading chaos in Bahrain” for its decision.