- Yemen's Iran-backed Shiite rebels will only commit to a ceasefire expected next week if loyalists and the Saudi-led coalition supporting them end their "aggression", their spokesman said on Saturday.

The ceasefire was announced by the government earlier this week to coincide with UN-mediated peace talks in Switzerland on Tuesday.

"We will stop (fighting) when the aggression against us stops," Mohammed Abdulsalam, spokesman for the Ansarullah party, told a news conference in the rebel-held Yemeni capital before heading to Switzerland for the talks.

"Based on what has been agreed, there will be a halt to the aggression on December 14 which will be confirmed within 24 hours before we begin a serious and positive dialogue," he said.

Foreign Minister Abdulmalek al-Mekhlafi told AFP "there is an agreement on a ceasefire to begin Monday."

"From our side, we wish a ceasefire would start even from now," said Mekhlafi, adding that he hoped the rebels, known as Huthis, would commit.

UN envoy Ismail Ould Cheikh Ahmed said this week that Riyadh had promised to observe the ceasefire and pause its aerial assault on rebel positions during talks.

A swift halt to the fighting, which has dramatically escalated since a Saudi-led coalition began bombarding insurgents in March, was imperative for those caught up in the conflict, he said.

The United Nations, citing data compiled from health facilities, says more than 5,800 people have been killed in Yemen, about half of them civilians, and more than 27,000 wounded since March.

- Escalation ahead of talks -

But coalition strikes and clashes between loyalists and rebels intensified across several parts of Yemen Saturday, military sources said.

"The rebels are attacking loyalist positions as the consultations approach," one of them said. "They are trying to make gains on the ground during this period."

The coalition pounded rebel positions in the eastern oil-rich Marib province and on the west coast in strategic Taez province overlooking the Red Sea, military and rebel sources told AFP.

In Daleh, 12 rebels and three pro-government fighters were killed as loyalists advanced on the province's second-largest city Damt, seized by rebels in November, military sources said.

Loyalists also advanced in Marib, taking several positions in western parts of the province, the sources said.

But late Friday, rebels recaptured the Shuraija region of Taez, military sources said. It links the province with Lahj in the south, home to the key Al-Anad air base where Arab coalition troops are deployed.

Four pro-government forces and three rebels died in the fighting, the sources added.

- Women delegates -

The talks are to be held for an indefinite period of time and away from the media in an undisclosed Swiss location. They will focus on four main areas, including the terms for a permanent ceasefire and the withdrawal of armed groups from the areas under their control, a reference mainly to the Huthis.

Participants will include Huthis, representatives of President Abedrabbo Mansour Hadi's internationally recognised government and officials from the General People's Congress party headed by former president Ali Abdullah Saleh.

Renegade troops loyal to Saleh have been fighting alongside the Huthis, who took control of Sanaa in September 2014 and swept south.

All three delegations have announced the names of their envoys to the talks.

Abdulsalam will lead the Huthis and Mekhalfi will lead the government delegation, while the GPC delegation will be headed by the party's secretary general, Aref al-Zoka.

The government and the GPC have each included a woman in their delegations, as per a UN request.

But women playing leading political roles are unheard of among the conservative Shiite Islamist Huthis.

AFP