Thousands of Yemenis have marched in the capital Sanaa to protest against an air strike which hit a funeral hall packed with hundreds of mourners, killing more than 140 people.
More than 500 people were also injured in the strike on Saturday, according to UN figures, which was one of the deadliest single attacks of the country's civil war.
Some of the demonstrators who marched outside the UN building in southern Sanaa blamed the organisation for not ending the conflict and urged an independent investigation. The Saudi-led coalition has been blamed for the air strike.
Some protesters brandished automatic weapons and rebel supporters in the crowd called on people from the region to rise up and attack Saudi Arabia.
The Saudi military announced on Sunday that it will launch an investigation into "reports about the regrettable and painful bombing" in Sanaa, without acknowledging that its coalition battling rebels in Yemen is the only force with air power in the conflict.
It is the latest in a string of bombings by the coalition that have struck hospitals, markets and other places where civilians congregate.
"The place has been turned into a lake of blood," said one rescuer, Murad Tawfiq.
Yemeni officials said the dead and injured includes military and security officials from the ranks of the Shiite Houthis rebels and their allies, loyalists of former president Ali Abdullah Saleh.
In an address on Yemeni state TV, Saleh called on citizens to head to the Saudi border and attack soldiers there to avenge the deaths. The rebel alliance is battling the internationally-recognised government of President Abed Rabbo Mansour Hadi.
Saturday's funeral was held for Sheikh Ali al-Rawishan, the father of Galal al-Rawishan, the interior minister in the rebel-led government. Among those killed was Maj Gen Abdul-Qader Hilal, head of the capital's local council, officials said, while Galal al-Rawishan was seriously injured.
The strike left the building little more than a shell, with most of its walls and roof gone. Cars parked outside were mangled by the blast.
Mohammed Abdul-Salam, the Houthi spokesman in Sanaa, angrily denounced the air strike as the latest act of "genocide" by the Saudi-led coalition.
"The silence of the United Nations and the international community is the munition of the murderers," he said. "Those murderers will not escape divine justice."
In its statement, Saudi Arabia said: "The coalition supporting the legitimate government in Yemen has announced that it is aware of reports about the regrettable and painful bombing of the Great Hall in Sanaa, which led to the killing and injuring of casualties, as reported.
"The coalition confirms that its troops have clear instructions not to target populated area and to avoid civilians."
Jamie McGoldrick, the UN humanitarian co-ordinator in Yemen, said in a statement that the relief community in the country is "shocked and outraged" by the air strikes.
He condemned the "horrific attack" and reminded all parties "that under international humanitarian law, they are obliged to protect civilians and civilian infrastructures". He called for an immediate investigation into the incident.
"The international community must exert pressure and influence on all parties to the conflict to ensure civilians are protected," he added said. "This violence against civilians in Yemen must stop immediately."
UN Secretary-General Ban Ki-moon condemned the bombing in a statement, saying that "any deliberate attack against civilians is utterly unacceptable... Those responsible for the attack must be brought to justice."
Foreign Office minister Tobias Ellwood said he would be raising the matter with the Saudi ambassador.
''I am deeply concerned by reports of an air strike hitting a funeral hall in the Yemeni capital Sanaa yesterday. The scenes from the site are shocking.
''I am raising my concerns with the Saudi ambassador to London today and urge the Saudi-led coalition's announced investigation into the incident to take place as a matter of urgency.
''There can be no military solution to this conflict. We urge all sides to recommit to political talks and to implement a cessation of hostilities.''
Shadow foreign secretary Emily Thornberry said: ''It cannot be right that, when faced with the conflict we see in Yemen - the scale of civilian casualties, and millions of children across the country facing starvation - the Government's primary diplomatic involvement is selling planes and weapons to the Saudi-led coalition, with no guarantees that they won't be used against civilians.
''Instead, Labour urges the Government to follow the lead of the United States in the wake of this attack, and urgently review its support for the Saudi-led coalition, as well as placing an immediate suspension on the sale of arms to Saudi Arabia until there has been a full and independent investigation into these attacks against civilians."