Saudi Arabia, Bahrain, the United Arab Emirates have broken diplomatic relations with Qatar, rattling a powerful 36-year-old Gulf states union, over what they say is the country’s support of terrorism.

Egypt has also cut off relations with the tiny Gulf state.

A statement on Saudi Arabia’s state news agency announced the move Monday morning, in order to “protect national security from the dangers of terrorism and extremism.”

“All ports of entry between the two countries would be closed,” according to the statement.

Saudi Arabia, the UAE, Bahrain, Oman and Qatar had formed a regional alliance known as the Gulf Cooperation Council. The union is viewed as one of the most influential in the Middle East.

Oman remains the only GCC member to maintain ties with Qatar.

Late last month, Saudi Arabia, the UAE, Bahrain and Egypt blocked several Qatari media outlets, including state-funded Al Jazeera, over comments allegedly made by Qatari Emir Sheikh Tamim Al Hamad Al Thani.

Al Thani reportedly hailed Iran as an “Islamic power” and criticized U.S. President Donald Trump’s policy towards Tehran.

The Emir’s comments appeared on Qatar’s official news agency, but Qatar claimed that the website was “hacked,” the report fabricated by the culprits.

Saudi Arabia and Iran are at odds over a number of regional issues, including Iran’s nuclear program and what Saudis see as Tehran’s growing influence in the kingdom’s sphere of influence especially in Syria, Lebanon and neighbouring Yemen.

“There are two competing theories,” Gayle Tzemach Lemmon, senior fellow at the Council of Foreign Relations says about the origin of the spat.

“One is that Saudi Arabia felt emboldened after Donald Trump’s visit, and Trump’s administration has had a strong stance on Iran, which is backed by Qatar.

“Another theory is that this is a product of month’s tension, all brought to a breaking point after the Qatar news agency hacking story.”

Trump recently visited the Saudi capital and addressed 55 Muslim leaders in a landmark speech urging them to double down on efforts to combat terrorism. CNN