A report by CNN says Federal Bureau of Investigation officials who analysed the content believe Russian hackers took control of the news agency, although it did not mention if the hackers were sponsored directly by the Russian government.
As many as seven countries-Bahrain, Saudi Arabia, the UAE, Egypt, Yemen, Libya's eastern-based government and the Maldives-have severed diplomatic ties with Qatar.
USA intelligence officials believe Russian hackers planted a false news story that led Saudi Arabia and several allies to sever relations with Qatar, prompting a diplomatic crisis, CNN reported Tuesday. Qatar hosts 8,000 US military personnel at al Udeid, the largest USA air base in the Middle East and a launchpad for US -led strikes on the Islamic State militant group.
"So good to see the Saudi Arabia visit with the King and 50 countries already paying off", he tweeted in reference to his trip to Riyadh last month. He offered no documents to support his claim, but Western officials long have accused Qatar's government of allowing or even encouraging funding of Sunni extremists.
"Perhaps this will be the beginning of the end to the horror of terrorism!"
Hours later, Trump urged unity in the Persian Gulf during a phone call with Saudi Arabian King Salman bin Abdul-Aziz al-Saud Salman. "The two leaders discussed the critical goals of preventing the financing of terrorist organizations and eliminating the promotion of extremism by any nation in the region".
Gabriel, who is due to meet Saudi Arabia's foreign minister on Wednesday, said he was surprised by the intensity of the tensions erupting in the Gulf region.
In a twist worthy of 007 movies, Qatar said it was a conspiracy, explaining that the news agency's site had been hacked and that "someone else" had posted negative comments about Saudi Arabia, the most powerful country in the Gulf.
Qatar's stock market rebounded in early trade on Tuesday after plunging the previous day but the Qatari riyal fell against the US dollar.
A Qatari official, however, said the rift was pushing Doha in the direction of leaving the six-state Gulf Cooperation Council, founded in 1981, "with deep regret".
Turkish President Tayyip Erdogan said isolating Qatar, including the use of sanctions, would not resolve any problems.
Traders on global markets anxious that Riyadh's allies would refuse to accept LNG shipments from the Gulf state, and that Egypt might even bar tankers carrying Qatari cargoes from using the Suez Canal as they head to Europe and beyond.
Such a decision should not come as a major surprise considering a series of events that started weeks ago, in the wake of negative comments about Saudi Arabia published by Qatar News Agency, a state-run Qatari news agency.