Saudi Arabia, Bahrain, the UAE, and Egypt announced that they have broken diplomatic relations with Qatar over Qatar's support for extremism and terrorism.  In addition, the Saudis have closed their sole land route into Qatar, while the other states have cut off air and sea routes into the tiny nation.

Although Qatar has had a troubled relationship with Saudi Arabia and other Gulf states in recent years, what apparently precipitated this drastic action was a series of tweets in late May from Qatari ruler Sheikh Tamim bin Hamad Al Thani that criticized the anti-Iranian policies of Saudi Arabia and other Gulf states belonging to the Gulf Cooperation Council.  The tweets were deleted, and the Qataris claimed that their website was hacked. 

The Saudis weren't buying it.  They may have been emboldened by the warm relations established between U.S. president Donald Trump and Saudi King Salman during the president's recent visit to the kingdom.  Not only did President Trump offer strong words of support for the Saudis, but the kingdom concluded a massive arms deal that could be worth more than $300 billion.

U.S. secretary of state Rex Tillerson described the row:

"What we're seeing is a growing list of some irritants in the region that have been there for some time," Tillerson said. "Obviously they've now bubbled up to a level that countries decided they needed to take action in an effort to have those differences addressed."

Monday's action is an escalation of a crisis that started shortly after Trump's last month trip to Saudi Arabia, where he and King Salman singled out Iran as the world's main sponsor of terrorism.

Those "irritants" include Qatari support for Houthi rebels in Yemen who are at war with Saudi Arabia, and their significant – but not decisive – support for the Muslim Brotherhood across the region.  Egypt is especially angry because the Brotherhood has been carrying out a low-level civil war against the government.

Times of India:

The official Saudi state news agency said Saudi Arabia had decided to sever diplomatic and consular relations with Qatar "proceeding from the exercise of its sovereign right guaranteed by international law and the protection of national security from the dangers of terrorism and extremism".

Saudi Arabia cut all land air and sea contacts with Qatar "and urges all brotherly countries and companies to do the same."

Bahrain's foreign affairs ministry issued a statement early Monday saying it would withdraw its diplomatic mission from the Qatari capital of Doha within 48 hours and that all Qatari diplomats should leave Bahrain within the same period.

The ministry's statement said Qatari citizens needed to leave Bahrain within two weeks and that air and sea traffic between the two countries would be halted. It wasn't immediately clear how that would affect Qatar Airways, one of the region's major long-haul carriers.

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.

The United Arab Emirates cut ties with Qatar, state news agency WAM reported, accusing its Gulf Arab neighbour of supporting extremism and undermining regional stability.

The Emirates cut ties and gave diplomats 48 hours to leave the country, citing their "support, funding and embrace of terrorist, extremist and sectarian organisations", WAM said.

Egypt said on Monday it cut ties with Qatar, accusing the Gulf Arab state of supporting "terrorist" organisations including the Muslim Brotherhood, Egypt's state news agency reported.

About 10% of Qatar's population is made up of Iranian nationals.  Qatar is a majority-Sunni nation, and it, like all the Gulf states, has a significant Shiite minority.  Qatar's policy of engaging Iran is based mostly on self-preservation, as the tiny nation, with a population the size of Houston, Texas, is extremely vulnerable.

Qatar is also considered the major sponsor and financier of terror groups in the region.

In 2013, the U.S. Treasury Department named Qatari citizen Abdul Rahman Bin Umair Al Nuaimi as a "Special Designated Terrorist."

Based on vetted and declassified information released by the U.S., Al Nuaimi, who once headed the Qatari Soccer Federation, transferred millions of dollars over a decade to Al Qaeda affiliates in Iraq, Syria, Somalia, Yemen and Lebanon. Al Nuaimi at one point ran a charity owned by a member of the Qatari royal family and donated $2 million a month to Al Qaeda in Iraq.

Khalifa Al Subaey, an Al Qaeda Qatari financier jailed for only six months in 2008 on terrorism charges and known for funding the mastermind behind 9-11, is once again raising money for terrorists in Syria and Iraq, according to a more recent designation by the U.S.

Those two dangerous men, Al Nuaimi and Al Subaey, are strolling freely in Qatar's malls and posting photographs of their expensive cars flanked by rare falcons and tigers.

Twitter also has a responsibility in flushing them out as they continue to post from ‎handles @binomeir ‎and@khalifasubaey.

It is not negligence or turning a blind eye. It is blatant state-sponsorship of terrorism.

Breaking off relations with Qatar may be a gambit by the Saudis to bring Shiekh al-Thani to heel, forcing his government to fall into line behind other states in the Gulf Cooperation Council to isolate the Iranians and join the military alliance against them.  It may also be an attempt to shock Qatar into eliminating its support for Houthi rebels and the Muslim Brotherhood.

There's a chance that Qatari defiance may escalate the situation, but it's more likely that cooler heads will prevail on both sides and the crisis will eventually blow over.