DUBAI, United Arab Emirates — Saudi Arabia and other Arab powers severed diplomatic ties Monday with Qatar and moved to isolate the energy-rich nation that is home to a major U.S. military base, accusing it of supporting terrorist groups and backing Iran.

The decision plunged Qatar into chaos and ignited the biggest diplomatic crisis in the Gulf since the 1991 war against Iraq.

Qatar, home to about 10,000 U.S. troops and the host of the 2022 FIFA World Cup, criticized the move as a “violation of its sovereignty.” It long has denied supporting militant groups and described the crisis as being fueled by “absolute fabrications” stemming from a recent hack of its state-run news agency.

Saudi Arabia closed its land border with Qatar, through which the tiny Gulf nation and international travel hub imports most of its food, sparking a run on supermarkets.

Bahrain, Egypt, Saudi Arabia and the United Arab Emirates began withdrawing their diplomatic staff from Qatar and regional airlines announced they would suspend service to its capital, Doha. Yemen’s internationally backed government, which no longer holds its capital and large portions of the war-torn country, also cut relations with Qatar, as did the Maldives and one of conflict-ridden Libya’s competing governments.

The move came just two weeks after U.S. President Trump visited Saudi Arabia and vowed to improve ties with both Riyadh and Cairo to combat terrorism and contain Iran. U.S. Secretary of State Rex Tillerson said the move was rooted in longstanding differences and urged the parties to resolve them.

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

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

The Gulf countries ordered their citizens out of Qatar and gave Qataris abroad 14 days to return home to their peninsular nation, whose only land border is with Saudi Arabia. The countries also said they would eject Qatar’s diplomats.

The nations also said they planned to cut air and sea traffic.