Saudi-led air strikes on a funeral in Sanaa killed more than 140 people and wounded more than 525, a United Nations official said.
However, sources in the Saudi-led coalition said there was no Arab coalition air role in the strike.
"Absolutely no such operation took place at that target," one of the sources said, citing what he described as confirmation from the coalition air force command.
"The toll is very high: more than 520 wounded and more than 100 martyrs," health ministry spokesman Tamim al-Shami told rebel television channel Almasirah.
He said the toll was likely to rise further as there were "charred human remains" that have yet to be identified and many people unaccounted for following the strikes on a building where mourners had gathered in southern Sanaa.
There was no independent confirmation of the toll.
Senior health ministry official Nasser al-Argaly earlier gave a toll of 82 killed and 534 wounded.
Witnesses said hundreds of people were attending the funeral of the father of rebel interior minister Jalal al-Rowaishan when the building was hit.
The Huthis did not say if Mr Rowaishan was present in the building at the time of the attack which they dubbed a "massacre" nor did they indicate if other senior figures were attending the funeral.
The Iran-backed Huthis swept into Sanaa in September 2014 and advanced across much of Yemen, forcing the internationally recognised government of President Abedrabbo Mansour Hadi to flee Sanaa.
More than 6,700 people - most of them civilians - have been killed in Yemen since the coalition intervened in support of Mr Hadi in March last year, according to the United Nations.