A statement from the National Security Council did not identify the Americans or detail the circumstances of their captivity or their release.
The White House said it had “worked tirelessly to secure the release” of the Americans since they were taken earlier this year. It cited its “deep regret” over the targeting of the residence and said the attack was “a clear violation of the charters and worldwide norms that emphasize the inviolability of diplomatic premises”.
The company, Transoceanic Development of New Orleans, confirmed that Darden had been freed.
The identities of the hostages were not immediately known.
A Saudi-led coalition has conducted air strikes on rebel positions across Yemen since March and has provided training and heavy weapons to forces seeking to reinstate exiled President Abedrabbo Mansour Hadi. The U.S. Ambassador to Muscat and a consular official met them upon arrival and will provide all possible consular assistance.
But the Shia Houthis opposes both Al-Qaeda and ISIS.
According to the rebels and anonymous officials at Sana’a global Airport, the six hostages were released after being held captive for the past five months.
The bulk of coalition troops are massed about 50 kilometres (31 miles) from Marib city waiting for “zero hour”, when they will move on the provincial capital, he said.
Another American, a journalist named Casey Coombs, also was detained by the Houthis but was released in June with the help of the Omani government.
Their release was negotiated by the Omanis, the USA administration official said and comes at a time of intensified diplomacy to try to end a war that has been raging for over six months and left almost 5,000 people dead – including 2,000 civilians, according the United Nations and to rights groups.
The foreign ministry also urged the Yemeni parties to put aside their differences with each other to ensure the return of stability and security in the country.
“I am not privy to that information if there was anything”, he said.