Wounded rebels were flown out of the Yemeni capital Sanaa on Monday for medical treatment, a critical step towards bringing warring parties to planned UN-brokered negotiations in Sweden.

The UN-chartered flight had taken off at 6:00 pm (1500 GMT) for Oman carrying 50 wounded rebels, their escorts and a team of doctors, a security source at Sanaa International Airport told AFP.

The United Nations' envoy to Yemen, Martin Griffiths, meanwhile landed in Sanaa on a separate plane to meet the Huthi rebels, who have been locked in a four-year conflict with a rival Saudi-led military coalition.

A UN source confirmed wounded rebels had been evacuated from the Yemeni capital in what was a "confidence-building measure" aimed at pushing ahead with negotiations between the Huthis and the coalition this month.

The evacuation marks a key step in kickstarting stalled negotiations as world powers press for an end to the devastating conflict that has pushed Yemen to the brink of famine.

Saudi Arabia and its allies, who back Yemen's embattled President Abedrabbo Mansour Hadi, had agreed to allow for the evacuation of 50 wounded combatants, 50 escorts and a team of Yemeni and UN doctors to the Omani capital early Monday morning -- a condition set by the Huthis for negotiations.

- Talks to include airport -

The fate of wounded rebels had been a stumbling block to the start of a previous round of aborted peace talks in Geneva in September.

The rebels had said they would attend the talks in Sweden if they were guaranteed safe passage.

Journalists were banned from Sanaa International Airport in the hours leading up to the departure of the UN flight on Monday.

Earlier in the day, wounded rebels were transported across the capital, controlled by the Iran-backed insurgents since 2014, in ambulances as they made their way to the long-defunct airport.

The proposed UN-brokered peace talks have been backed by both the rebels and the government and were expected to take place in Sweden this week.

UN Secretary-General Antonio Guterres, however, has played down the early December schedule and said he hoped talks would start "this year".

A UN source said the reopening of Sanaa airport, shut for more than three years following air raids by the Saudi-led coalition, was a priority at the next round of peace talks.

The Huthis had announced at the weekend that the airport could now meet the requirements of the International Civil Aviation Organization (ICAO) to "receive civilian flights".

The ICAO has not released a statement on Sanaa airport.

A UN panel of experts this year said the "effective closure" of Sanaa airport since 2015, when the Saudi-led alliance intervened in the Yemen war, constituted a violation of international humanitarian law.

- 'No excuses' -

The opposing sides cautiously reiterated their willingness to attend negotiations.

Yemen's information minister, Moammer al-Eryani, said the government had agreed to the Sweden talks as a first step towards "facilitating negotiations" and to end "all excuses invoked by the coupists (rebels) to evade finding peace".

Huthi military spokesman Yahya Saree said the rebels were ready to hold talks "starting with a ceasefire" by the rival coalition at a press conference broadcast on the insurgents' Al-Masirah television.

Iran also offered support on Monday, saying it was ready to cooperate with the international community to resolve the crisis.

Previous talks planned for September in Geneva failed to get under way as the Huthi delegation never left Sanaa, saying the United Nations could not guarantee their safe return.

The rebels also accused the world body of failing to secure the evacuation of wounded rebels to Oman, a relatively neutral party in the Yemen war.

Talks initially broke down in 2016, when 108 days of negotiations in Kuwait failed to yield a deal and left rebel delegates stranded in Oman for three months.

UN aid chief Mark Lowcock warned last week that Yemen was "on the brink of a major catastrophe".

His comments followed renewed deadly clashes between Huthi rebels and pro-government forces in the Red Sea port city of Hodeida, which is vital for the flow of humanitarian aid and controlled by the rebels.

The coalition spokesman said Monday that military operations in Hodeida were "ongoing".

The United Nations has described Yemen as the world's worst humanitarian disaster, with at least 10,000 people killed since the coalition intervened in 2015.

Rights groups fear the actual toll is far higher.

AFP