"The plane has just taken off in Sanaa".
The UN Envoy for Yemen Martin Griffiths hailed that "I welcome the start of the prisoners release as agreed by the parties in September in Switzerland and in line with commitments made in Stockholm".
According to the deal reached in Switzerland last month, a total of 1,081 war prisoners will be released on Thursday and Friday.
Two Americans have been freed and the remains of a third American have been released by the Houthis, an Iran-backed rebel group in Yemen, as part of an exchange, national security adviser Robert O'Brien confirmed Wednesday.
"The transaction will be executed, with God's help, on the scheduled dates today and tomorrow", Abdel Kader Mortaza, the rebel official in charge of prisoner affairs, said in a tweet. Planes carrying prisoners took off from three airports in an operation that involved about 1000 prisoners.
One of the aeroplanes was carrying Saudi and Sudanese detainees and flew to Saudi Arabia.
"It's going to be a great day", said Fabrizio Carboni, the Middle East director for the International Committee of the Red Cross, which is helping coordinate the complex operation.
The ICRC plane carrying the freed government soldiers arrived in the government-held Sieyun city in the southeast of the country afternoon.
Man decapitated near Paris, anti-terror probe under way: prosecutors
He said the victim was murdered because he was a teacher and taught freedom of expression , after Macron visited the scene. France has over the past several years seen a series of violent attacks carried out by religious extremists.
On Wednesday, two United States citizens were released from Houthi custody.
Houthi spokesman Mohammed Abdulsalam said on Thursday the swap "brings hope for peace-building".
"We're doing everything we can to provide our diplomatic support as Saudi Arabia works to try and come to a better solution inside of Yemen", Pompeo said.
Yemen has been devastated by a conflict that escalated in March 2015, when the rebels seized control of much of the west of the country and forced President Abdrabbuh Mansour Hadi to flee overseas.
On Friday 352 prisoners were exchanged after more than 700 were swapped on Thursday - including a plane carrying Saudis and Sudanese to Riyadh - said the ICRC, which managed the process.
The White House announced the release of U.S. citizens Sandra Loli and Mikael Gidada, saying that the two had been held captive by the Iranian-backed Huthi rebels who control much of Yemen including its capital Sanaa.
Robert O'Brien, the US national security adviser, thanked Saudi King Salman bin Abdulaziz and Omani Sultan Haitham bin Tariq Al Said "for their efforts to secure the release of our citizens".
Yemen has been mired in conflict since the Houthis ousted the internationally recognised government from power in Sanaa in late 2014, prompting the Western-backed coalition to intervene in March 2015.