SANAA, Yemen — A plane carrying some 50 Shiite rebels wounded in fighting in Yemen's civil war left Monday for neighboring Oman where they will receive treatment, according to officials, in a move that meets one of the conditions set by the rebels to participate in peace talks.

Their evacuation aboard an Ethiopian Airways flight from the rebel-held capital, Sanaa, could also be a prelude to the departure by rebel delegates later this week to Sweden where peace talks are due to take place in the latest diplomatic bid to end Yemen's civil war.

The officials said U.N. Special Envoy to Yemen Martin Griffiths arrived earlier on Monday in Sanaa, where he was expected to hold last-minute talks with the rebels, known as Houthis.

The officials spoke on condition of anonymity because they were not authorized to brief the media. They said Griffiths will likely leave for Sweden on Tuesday with the rebel delegates.

The United Nations says Yemen's internationally-recognized government and the rebels have agreed to attend the peace talks, but the Houthis have said they will only attend if safe travel is guaranteed.

The conflict in Yemen began with the 2014 takeover of Sanaa by the Houthis, who toppled the government of President Abed Rabbo Mansour Hadi. A Saudi-led coalition has been fighting the Houthis since March 2015.

Saudi-led airstrikes have hit schools, hospitals and weddings, and the Houthis have fired long-range missiles into the kingdom and targeted its vessels in the Red Sea. Tens of thousands of people are believed to have been killed in the war, which has pushed Yemen to the brink of famine.