By Mohammed Ghobari

SANAA (Reuters) - The death toll from an air strike on a wedding party in Yemen has jumped to 131, medics said on Tuesday, in one of the deadliest attacks on civilians in Yemen's war that drew strong condemnation from the U.N. secretary-general.

A Saudi-led Arab coalition that has air supremacy over Yemen has strongly denied any role in the wedding party carnage, and a coalition spokesman suggested that local militias may have fired the projectiles.

The U.S.-backed coalition has been targeting the Iranian-allied Houthis mostly by air across Yemen since March with the goal of ousting the war's dominant armed faction from regions it has seized since last year, including the capital Sanaa in the north, and to restore President Abd-Rabbu Mansour Hadi.

Residents said on Monday that two missiles tore through tents in the Red Sea village of Al-Wahijah, near the ancient port of Al-Mokha, where a local man affiliated with the Houthi group was holding his wedding reception.

The area is deemed the gateway to the Bab al-Mandeb strait connecting the Red Sea with the Arabian Sea, a vital route for oil tanker and other maritime traffic between Asia and Europe.

A resident of Al-Wahijah had said on Monday that 12 women, eight children and seven men had died in the air strike, and a local official put the death toll at 30.

On Tuesday, a medical source at Maqbana hospital, where most of the casualties were taken, said the death toll had climbed to 131 people, including many women and children.

The United Nations and international rights groups have expressed alarm at the escalating number of civilian deaths in Yemen - at least 2,355 out of more than 4,500 people killed from the end of March to Sept. 24, according to figures released by the U.N. human rights office in Geneva on Tuesday.

Secretary-General Ban Ki-moon condemned the high death toll at the wedding event and warned that any intentional attack on civilians violates international law and must be investigated.

ARAB COALITION DENIAL

Arab coalition spokesman Brigadier-General Ahmed al-Asseri said there had been no air operations in the area in the al-Mokha area for three days so "this is totally false news".

He added that the coalition would concede a mistake if it made one but Yemen's conflict was chaotic with a grab bag of armed groups active, and that civilians sometimes could not differentiate between cannon, mortar and Katyusha rocket fire.

In Geneva, U.N. human rights office spokesman Rupert Colville said it had a team on the ground in Yemen trying to verify details of the wedding party bloodshed.

“The (Hadi-led) government in exile seemed to have acknowledged it and said it was a mistake ... I don't think we have much doubt that this incident took place and it is a grave incident," Colville told a news conference.

He also said the coalition’s naval blockade of Yemen’s main seaports was exacerbating a humanitarian crisis in Yemen. World Food Programme spokeswoman Bettina Luescher said 10 of Yemen’s 22 governorates were so short of food that famines were looming.

The United States is the main arms supplier to the Gulf Arab coalition. In April, U.S. officials said Washington was expanding intelligence-sharing with Saudi Arabia to provide more details about potential Houthi targets.

Al-Wahijah is located in Taiz province, which the Houthis captured in March as they began advancing on the strategic southern port city of Aden, to which Hadi had decamped after losing Sanaa, before he was forced to flee to Saudi Arabia.

Gulf-backed forces retook Aden in July, allowing Hadi to re-base there after six months of exile in Riyadh, before thrusting northwards to take on the Houthis in Taiz and ultimately Sanaa.

For Hadi’s Sunni Gulf Arab patrons, returning him to Yemen represented a moment of vindication for what they see as a wider struggle against expansionary meddling in the region by Iran's Shi'ite Muslim theocracy, a charge Tehran denies.

On Sunday, residents and medics said helicopters flying from Saudi Arabia attacked a village in the northern Yemeni province of Hajjah, killing at least 30 people. Saudi authorities dismissed this report as "totally false" too, while U.N. rights spokesman Colville said the details were being checked.

The air strike campaign has resulted in several mass killings of civilians, including 36 people at a water bottling plant in August and 25 workers at a milk factory in April.

Around 100 Saudi soldiers and security personnel and some 30 civilians have also been killed in cross-border fire into southern Saudi Arabia by Houthis and allied troops loyal to former president Ali Abdullah Saleh.

In the latest such attack, the Saudi interior ministry said on Tuesday one of its servicemen had been killed in the southern Jizan region by projectiles fired on Monday from Yemen.

(Additional reporting by William Maclean, Hadeel al-Sayegh and Marwa Al-Malik in Gulf region, Stephanie Nebehay in Geneva; Writing by Sami Aboudi; Editing by Mark Heinrich)