Two US citizens, one British national and three Saudis held for months by Yemen's Houthi group, have been freed and have arrived in Oman, according to British and Omani officials as well as Houthi sources.
Their release appeared to be a goodwill gesture before talks between Houthis and the UN envoy to Yemen on efforts to end nearly six months of fighting.
Monday marks one year since the Houthis stormed the capital Sanaa.
Oman's foreign ministry said in a statement it had worked with Yemeni authorities in Sanaa to ensure the release of the Americans held by the Iran-allied Shia Houthis.
The ministry statement, carried by ONA state news agency, said the three Saudi nationals and the Briton were also freed and flown to Muscat aboard the same flight.
The three Westerners had been held by the Houthis since the early days of a Saudi-led military campaign in March on charges of entering the country without proper visas.
The White House said the release of the two Americans was arranged with the help of Oman's Sultan Qaboos.
A spokesman for the US National Security Council also called for the immediate resumption of peace talks aimed at ending the fighting in Yemen.
A third US captive was still believed to be held by Houthi fighters, according to a person familiar with the matter.
Britain's foreign office confirmed that a British national had travelled to Oman from Yemen and said that embassy staff had met the flight. It gave no further details.
Earlier, the leader of the Houthis said his group remained open for a political settlement to end the conflict but would resist what he called Saudi-led aggression.
"We call on our people, all strata of our people, to maintain their moves to confront this criminal aggression," Abdel-Malik al-Houthi said in a speech on Sunday, adding that "political solutions were still possible".
Friday marked six months since the beginning of the Arab coalition's air strikes inside Yemen.
More than 4,500 people have been killed in the fighting since March, according to UN figures.