Saudi-backed forces loyal to Yemen's exiled government have announced the recapture of Abyan province in a southern offensive that has seen key gains against the Houthi rebels.

Military officials who back President Abd-Rabbu Mansour Hadi said on Tuesday that loyalist forces have retaken Loder, the last town in Abyan to fall from Houthi hands. "Abyan is now completely free" of the Shia rebels, one official said.

Al Jazeera's Hashem Ahelbarra, reporting from Doha, described the development as "quite significant".

"There is only one province in the south that is still under the control of the Houthis. Once they control the south, it is going to be quite massive, because then the government in exile is going to return ... they will set up ministries, establish a base, from where they can continue the fight to control the capital," our correspondent said.

The latest loyalist gains came as seven pro-government activists were handed over in Yemen's second city, Aden, as part of a prisoner swap overseen by the International Committee of the Red Cross.

Loyalists had already taken Abyan provincial capital, Zinjibar, from the rebels and their allies on Sunday, as they pressed an advance from Aden.

Backed by a Saudi-led coalition that has been carrying out air strikes since March, pro-government forces have been battling for months to restore President Hadi, in exile in Riyadh, to power.

The officials were unable to provide details on the number of loyalist or rebel casualties in the fighting.

Yemen is "crumbling" under a deepening humanitarian crisis after months of civil war, the head of the ICRC said on Tuesday.

Peter Maurer, ending a three-day visit to the Arabian Peninsula country, called for free access to deliver life saving food, water and medicines, while urging the warring parties to work towards a negotiated solution.

"The humanitarian situation is nothing short of catastrophic. Every family in Yemen has been affected by this conflict... The world needs to wake up to what is going on," Maurer said in a statement.

On Monday, the international group Doctors Without Borders (MSF) said it has treated more than 10,000 war-wounded in Yemen and that aid groups were being overwhelmed by the country's massive humanitarian needs.

Thierry Goffeau, coordinator of the group in Aden, said that hospitals were overcrowded and were being forced at times to turn away patients.

Nearly 4,000 people have been killed and 1.3 million forced to flee their homes during the conflict, he said.

The crisis in Yemen descended into civil war in March when Houthi forces, who had seized the capital Sanaa, advanced south towards Aden, forcing Hadi to flee to Saudi Arabia.

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Humanitarian groups say emergency services are struggling to assist the needy in Yemen [Reuters]

Aljazeera