He said 21.2 million people, or 82 percent of the country's population, require some kind of humanitarian assistance. Fourteen million people lack sufficient access to health care. And 1.8 million children have been out of school since the conflict began.
"Nearly 320,000 children are acutely malnourished," he added.
He did not say how many civilians were among the 5,700 killed during the conflict. The U.N. human rights office in late October reported that more than 2,600 civilians had been killed so far, about two-thirds of them by airstrikes.
Since March, a coalition led by neighboring Saudi Arabia and backed by the United States in support of Yemen's internationally recognized government has been fighting Iran-backed Houthi rebels who had seized large parts of the country, including the capital, Sanaa.
The international community has pleaded for months for the coalition to ease restrictions on crucial commercial imports such as fuel and medical supplies. Van Der Klaauw said supplies of fuel, food, medicines and other supplies were dangerously low, while food prices have soared.
The conflict also has severely hurt international efforts to get aid to many places around Yemen.
The U.N. humanitarian coordinator said that about 120,000 people have fled the country during the fighting, and about 2.3 million people have fled their homes.
In addition, he noted that more than 8,800 human rights violations have been verified since the conflict began.
Last month, Human Rights Watch accused the U.N. Human Rights Council of failing to set up a fact-finding mission to scrutinize abuses in Yemen, saying members backed down under "intense pressure from Saudi Arabia."
The Associated Press