Four Arab nations cut diplomatic ties to Qatar early Monday morning, and Bahrain has given citizens 14 days to leave the country.
The decision further deepens a rift between Gulf Arab nations over Qatar's support for Islamist groups.
Bahrain, Egypt, Saudi Arabia and the United Arab Emirates all announced they would withdraw their diplomatic staff from Qatar, a gas-rich nation that will host the 2022 FIFA World Cup.
Saudi Arabia said the move was made for the "protection of national security" and Qatari troops would be pulled from its ongoing war in Yemen.
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.
It has reportedly given Qatari residents 14 days to leave Bahrain.
All the nations also said they planned to cut air and sea traffic to the peninsular country.
It wasn't immediately clear how that would affect Qatar Airways, one of the region's major long-haul carriers.
Qatari officials did not immediately respond to a request for comment.
The decision comes after Qatar alleged in late May that hackers took over the site of its state-run news agency and published what it called fake comments from its ruling emir about Iran and Israel.
The Qatari News Agency report claimed Qatar had withdrawn its ambassadors from Bahrain, Egypt, Kuwait, Saudi Arabia, and the UAE because of "tension" with the administration of US President Donald Trump.
Trump visited the region two weeks ago and met with Qatar Emir Sheikh Tamim bin Hamad al-Thani.
The article also quoted the Qatar Emir saying Iran was an "Islamic power" and Qatar's relations with Israel were "good."
Its Gulf Arab neighbours responded with anger, blocking Qatari-based media, including the Doha-based satellite news network Al-Jazeera.
Qatar has long been at odds with its neighbours over its support for the Muslim Brotherhood and its close relations with Iran.
- With AP