Local supermarkets described residents stocking up on emergency supplies over fears of food shortages.
Qatar has an independent streak that has often angered its neighbours. It began after Saudi forces carried out an attack on Qatari border guards which left three dead including one Saudi soldier.
In addition to cutting diplomatic relations, the countries that acted Monday said they would withdraw their diplomatic staff from gas-rich Qatar and cut air and sea traffic to the country.Qatar Airways announced a suspension of flights to Saudi Arabia. Bahrain, Egypt, Yemen and the Maldives were also among the governments that severed ties.
Qatar, which has a population of 2.5 million people, is largely dependent on imports of foodstuffs to meet its needs.
In 2014, Saudi Arabia, the UAE and Bahrain temporarily withdrew their ambassadors from Qatar, accusing it of breaching a regional security pact. Consumption is traditionally higher during the Muslim holy month of Ramadan, which is now being observed. "One of its pitches [to secure World Cup] was that Qatar is one of the most stable nations in the Middle East".
Qatar's stock market rebounded in early trade on Tuesday after plunging the previous day but the Qatari riyal fell against the United States dollar. Labor Secretary Silvestre Bello said the ban took effect Tuesday, but there is no plan yet to repatriate the more than 200,000 Filipino workers in Qatar.
There were already signs of emerging difficulties.More news: Why the Cleveland Cavaliers will win the NBA Finals
Some Saudi Arabian and UAE commercial banks were also shunning Qatari banks, holding off on letters of credit, banking sources told Reuters on Tuesday. "The situation as it now stands is like a siege".
"Qatar Airways serves 18 destinations in these four countries, accounting for approximately 18% of the airline's total seating capacity", said Rob Watts, managing director at Aerotask, a global aviation consultancy firm.
Several Gulf ports have stopped Qatari registered vessels or those heading to the peninsula from docking. Analysts say the unprecedented diplomatic rift is also driven by the belief that Qatar is too closely aligned with Iran.
Qatar is a nation of 2.5 million with a U.S. military base and the Qatar government has been denying reports that it is supporting militants.
Sheikh Sabah Al Ahmad Al Sabah flew out of Kuwait City on Tuesday afternoon, heading for Jiddah, Saudi Arabia.
Trump's harsh words for the Qataris were a departure from his rhetoric during his visit to Saudi Arabia, when he met with Qatar's emir and called the relationship "extremely good".
Qatar expressed regret over this decision calling it groundless.