US hostage Casey Coombs released in Yemen and flown to Oman
One of four Americans held by Houthi rebels in civil war-torn Yemen has been released, the US State Department says.
Casey Coombs, a freelance journalist, was flown to Oman where he was met by the US ambassador.
Last week, the Washington Post reported that at least four Americans were being held by Houthi rebels.
Meanwhile, a video of a Frenchwoman kidnapped in February has been posted, in which she appeals for efforts to be made to secure her release.
Isabelle Prime, who worked as a consultant on a World Bank-funded project, was seized with her translator, who was later freed, as they were driving to work in the capital, Sanaa.
She called for French President Francois Hollande and Yemeni President Abed Rabbo Mansour Hadi to help secure her release, saying: "Please bring me to France fast because I am really, really tired."
A French official has confirmed the authenticity of the video, but the identity of her captors remains unclear.
Mr Coombs, who wrote for the news website the Intercept, was captured in Yemen several weeks ago.
In April he reported that he was having difficulty leaving the country, "like hundreds - and possibly thousands - of other American citizens".
US State Department spokeswoman Marie Harf said Mr Coombs had arrived safely in Oman following his release and was in a "stable condition".
"We are grateful to the government of Oman and personally to Sultan Qaboos for assisting with the safe passage of a US citizen to Oman," she added.
She declined to provide any further details, but said the US was doing everything possible to secure the freedom of the other American citizens being held in Sanaa.
Mr Coombs' mother, Jill Hammill, told the Washington Post she was "overjoyed" by her son's release.
The Oman News Agency said a Singaporean citizen was also evacuated from Yemen on Monday and taken to the Omani capital Muscat.
Oman has been brokering talks between the Houthis and the United States to put an end to Yemen's civil war.
The Houthis and army units loyal to Yemen's former leader, Ali Abdullah Saleh, overran Sanaa in September last year and are now in control of several other cities.
In December, US journalist Luke Somers and South African teacher Pierre Korkie died during a failed attempt by US commandos to rescue them from an al-Qaeda hideout in south-eastern Yemen.
The UN says two months of fighting and air strikes have left at least 1,037 civilians dead, including 130 women and 234 children, and displaced half a million others.
There has also been massive destruction of civilian infrastructure, and a sea and air blockade has caused severe shortages of food, water, medicine and fuel.