"I was living and working in Yemen and was in prison for 899 days, 2 years and 6 months, in solitary confinement and it was hell," said one U.S. citizen.

Two United States citizens and the remains of a third have been released by Iran-backed militants in Yemen, U.S. officials have said.

American citizens Sandra Loli and Mikael Gidada were released from Houthi custody Wednesday, National Security Advisor Robert C. O'Brien said in a statement.

“We send our condolences to the family of Bilal Fateen whose remains will be repatriated as well,” he added, in an apparent reference to the dead U.S. citizen.

The Wall Street Journal was the first to report on the news, describing the release as part of a U.S.-backed trade that returned more than 200 Houthi loyalists to the war-ravaged nation. The State Department did not comment on a possible trade, and NBC News has not independently confirmed that the Americans' release was part of such a deal.

Oman’s state news agency reported that following royal directives, the American citizens were flown out of the Yemeni capital Sanaa to the Omani capital of Muscat on board two Royal Air Force of Oman flights. It added that a group of Yemeni patients who had been treated in the Gulf state were also repatriated. NBC News was not able to confirm these reports.

A news agency affiliated with the Houthi rebels, who have been fighting a Saudi-led coalition allied with the internationally recognized government since 2015, said Thursday that 283 wounded Houthis had returned to Yemen from Oman.

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O'Brien did not mention any exchange, but thanked the leaders of Oman and Saudi Arabia for their help in securing the release of the Americans.

U.S. officials gave little information about the three hostages but Kash Patel, a deputy assistant to President Donald Trump, told the Wall Street Journal that Loli, a humanitarian worker, had been held hostage for 16 months and Gidada, a businessman, had been held for more than a year. NBC News has not independently verified all of this reporting.

"I was living and working in Yemen and was in prison for 899 days, two years and six months, in solitary confinement and it was hell, it was really hell. Bad, bad experience," Gidada told Oman TV on arriving in Muscat.

Both Gidada and Loli thanked Oman's sultan.

"I am so so appreciative and I'm so happy today," Loli told Oman TV.

Secretary of State Mike Pompeo said in a statement that Wednesday’s news was “the latest affirmation that President Trump remains committed to bringing every American held hostage or wrongfully detained abroad back home.”

The Iran-backed Houthi rebels took control of Sanaa from the internationally recognized government in 2014 and a Saudi-led military coalition intervened against the rebels the following year.

Since then more than 112,000 people are estimated to have died as a direct result of the violence, including more than 12,000 civilians killed in targeted attacks, according to The Armed Conflict Location and Event Data Project.

Millions more are suffering from food shortages in the world’s worst humanitarian crisis, according to the United Nations. An estimated 80 percent of Yemen’s population are reliant on aid, according to the International Committee of the Red Cross, with people being forced to choose between food and medicine.