RIYADH - Only a comprehensive solution involving all parties to the Yemen crisis can resolve the conflict, the UN envoy to the war-ravaged country said Sunday at a conference boycotted by rebels.

"There is no solution to this crisis but with a comprehensive dialogue that will not exclude anyone," Ismail Ould Sheikh Ahmed told the meeting of Yemeni political parties, intellectuals and civic groups in the Saudi capital.

The Mauritanian diplomat is seeking to restart Yemeni peace talks after weeks of war that have affected millions of people.

He called on all parties in Yemen to take part in a future conference "without any preconditions".

The Huthi rebels are fighting forces loyal to exiled President Abedrabbo Mansour Hadi and have seized large parts of Yemen including the capital Sanaa.

They want talks held in Yemen and stayed away from the three-day meeting which organisers said drew about 400 delegates, some wearing daggers and traditional headgear. Yemen's Vice-President Khaled Bahah told AFP that, despite their absence on Sunday, he expected the Huthis would attend future talks.

"They have chosen to be out of this conference but, at the end, they will be coming," he said.

Hadi, in a rare public address since the war drove him into Saudi exile, repeated accusations that the rebels had committed a "coup" and abuses against the population.

"We are trying to regain our nation" from militias backed by "external" forces, he said in a reference to Iran, which has denied arming the rebels.

"By God's will, victory will be near," vowed Hadi, who convened the conference held in conjunction with the six-nation Gulf Cooperation Council.

"We are coming back to Aden and Sanaa... We are coming back to build a new, united federal Yemen," Hadi said.

Transport Minister Bader Ba-Salama told AFP that among the participants is the Southern Movement, an umbrella group from the former South Yemen which was independent until 1990.

The Huthis are allied with fighters loyal to former president Ali Abdullah Saleh, whose General People's Congress party "has many of its leaders taking part" in the conference, said Abdulaziz al-Jaber, head of the organising committee.

Saleh himself is under US and UN sanctions and the conference will not deal with him, Jaber said on Saturday.

Among the meeting's goals is working towards a constitution which would be presented to the Yemeni people, "and to hold a referendum to put the results of the dialogue into practice", he said.

Britain's ambassador to Sanaa, Edmund Fitton-Brown, speaking for a group of 14 ambassadors, told the meeting they expect that the UN envoy will, "in consultation with all parties, propose a course to implement the recommendations of this conference".