UN-sponsored talks between Yemen's exiled government and Houthi rebels are in doubt over the make up of the delegations. Saudi-led coalition airstrikes have continued in Yemen.
Airport officials at Sanaa International Airport said that the UN plane meant to carry Shiite Houthi rebels and their allies to Geneva had left empty on Saturday.
Representatives of the Houthi rebels and former President Ali Abdullah Saleh's General People's Congress refused to board the plane because it was scheduled to stop off in Jizan, Saudi Arabia, a Houthi official said.
A Houthi representative said that they also objected to the idea of two separate delegations to the talks, one representing the embattled government, and one seen as representing a "coup."
The UN said on Friday that the start of the talks would be delayed until Monday "due to unforeseen circumstances" delaying the arrival of one of the delegations.
UN Secretary General Ban Ki-moon said the talks were aimed at securing a ceasefire, agreeing on a withdrawal plan for the Houthis and increasing humanitarian aid deliveries.
Ongoing air attacks
Yemeni security officials said six civilians were killed and dozens injured in Saudi-led coalition airstrikes in Sanaa on Saturday. The attacks appear to have targeted the areas around the homes of two brothers and a nephew of former President Saleh.
Military units loyal to Saleh have aligned themselves with the Shiite Houthi rebels.
The Saudi-led coalition began its airstrikes on March 26 in support of Yemen's President Abed Rabbo Mansour Hadi. Hadi had fled the capital for Aden before leaving for exile in Saudi Arabia, in reaction to the Houthi rebel advance.
The delegation representing the Hadi government arrived in Geneva Saturday morning, an official from his office said.
The World Health Organization said on Friday that 2,584 people had been killed in fighting in Yemen up to June 7. A further 11,065 had been wounded.
jm/bk (AFP, AP)