Saudi Arabia has announced it is severing all diplomatic ties with Qatar amid an intensifying dispute that has pitted Gulf Arab states against the small oil-rich country. In an announcement Monday on state-run television, Saudi leadership said it has already pulled Qatari troops from the war in Yemen, and separate news reports said Qatari citizens were ordered out of the country within 14 days. All land, air, and sea routes with Qatar were also cut off, with Saudi Arabia urging “all brotherly countries and companies to do the same.” The official state news agency said the decision was made for the sake of “national security from the dangers of terrorism and extremism.” The move comes after Bahrain made a nearly identical announcement earlier Monday, ordering Qataris out and cutting all transportation links between the two countries. Bahrain accused Qatar of backing terrorism and meddling in its internal affairs. United Arab Emirates and Egypt quickly followed suit, announcing the news within minutes of each other on state-run television.

Qatar has been at odds with its Gulf Arab neighbors ever since hackers allegedly published damning remarks falsely attributed to the emir of Qatar last month. Qatar has maintained that the comments were made up and blamed the incident on a “shameful cyberattack,” though its neighbors say the cyberattack revealed support for terrorism among the Qatari leadership. U.S. Secretary of State Rex Tillerson chimed in on the brewing crisis during a visit to Sydney on Monday, saying the spat was the result of “differences” between Gulf states that had “bubbled up.” Tillerson urged the Gulf states to work out their differences and remain united, saying the U.S. was willing to assist in negotiations.