UN-brokered peace talks between Yemen's internationally recognized government and the country's Shia rebels started on Tuesday in Switzerland.
The difficulty of the task is being underscored by rebel fighters' failure to honour a weeklong ceasefire in some parts of the country.
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The ceasefire scheduled to start at noon on Tuesday was meant to give the warring factions a chance to find a solution to the conflict that has collapsed the Arab world's poorest country. However, rebel shelling and ground clashes continued in the southwestern Taiz province, said security officials who remain neutral in the conflict that has splintered the country.
Airstrikes by a Saudi-led coalition targeting the rebels, however, have halted, they said, speaking on condition of anonymity because they were not authorized to brief reporters.
Yemen has been torn by fighting pitting the rebels, known as Houthis, and army units loyal to former President Ali Abdullah Saleh against an array of forces, including the internationally recognized government, which is backed by the Saudi-led coalition and supported by the United States, and also southern separatists, religious extremists and other militants.
In a statement, UN special envoy for Yemen Ismail Cheikh Ahmed said the talks in Switzerland "should mark the end of military violence in Yemen."
"The people of Yemen are daily, indeed hourly, anticipating the outcome of these discussions. This meeting is their only glimmer of hope and must not be extinguished," the envoy said in his opening remarks. "The tongues of fire, the scenes of destruction, the reverberation of bombs and the soaring prices have turned their daily lives into a series of ongoing tragedies."
In Geneva, UN spokesman Ahmad Fawzi said a total of 24 people were taking part in the "open-ended" talks.
According to the UN, the war in Yemen has killed at least 5,884 people since March, when the fighting escalated after the Saudi-led coalition began launching airstrikes targeting the rebels.
Just hours before the scheduled start of the ceasefire, the coalition and pro-government forces seized the Red Sea island of Zuqar from the rebels.
Yemeni security officials, who have remained neutral in the conflict, said both sides had intensified the fighting to solidify their positions ahead of the truce. There was no immediate word on casualties and the officials spoke on condition of anonymity because they were not authorized to speak to reporters.
Past efforts to end the violence have ended in failure, as the government insisted the Houthis comply with a UN resolution that requires them to return seized weapons and territory they had captured over the past year, including the capital, Sanaa. In response, the Houthis demanded negotiations over the country's political future.
The two sides had initially agreed to halt fire at midnight Monday but the coalition delayed the truce to midday Tuesday, without elaborating.
At training centre
Both sides of the conflict confirmed permission for "unconditional movement of supplies, personnel and teams to all parts of the country" during the ceasefire, the World Health Organization's mission chief for Yemen told reporters in Geneva on Tuesday. It was not immediately clear if deliveries were affected because of the fighting in Taiz.
Dr. Ahmed Shadoul said the WHO had 19 supply trucks ready to move in the Yemeni cities of Sanaa and Aden. Shadoul said 150 metric tons of supplies across the Red Sea in Djibouti could be delivered by next week.
The talks were taking place at the Swiss Olympic House in the village of Macolin, a training centre for elite athletes. Outside the two buildings at the sports center, police armed with automatic weapons were on patrol and they cordoned off the facility with metal barriers — requiring journalists to keep about 50 metres away.