Fighting has escalated around Yemen's key port city of Hodeida, with more than 150 combatants killed over the weekend from both the rebel and government-backed sides, officials said Sunday.

Airstrikes and naval artillery pounded rebel positions around the Red Sea costal city, where government backed-troops are launching a major ground assault in an attempt to wrest it from dug-in rebels. The officials spoke on condition of anonymity for fear of reprisals.

Fierce fighting also erupted in the provinces of Bayda, to the south, and Saada, a Houthi stronghold in the north, they added.

Yemen has been at war since March 2015 when the rebels, known as Houthis, occupied northern regions and forced the government into exile. Since then, a Saudi-led, U.S.-backed coalition supporting the largely exiled government has blockaded the rebel-held north and waged a devastating air campaign, causing thousands of deaths. The U.S. has sold billions of dollars' worth of arms to Saudi Arabia and provides logistical and other support to the coalition, while the coalition, which backs the exiled government, accuses the Houthis of acting as Iran's proxy.

The war has led to a humanitarian crisis that is one of the worst in the world, with three quarters of Yemen's population requiring some form of life-saving assistance and protection, according to the United Nations Population Fund. An estimated 10,000 people have been killed and more than 8 million are at risk of starvation from a looming famine, including 2 million mothers who are risking death.

The United Nations Children's Fund regional director said over the weekend that Yemeni authorities — both from the pro-government and rebel side — are making it "impossible" to deliver and distribute much-needed humanitarian aid to the country.

On Sunday, Geert Cappelaere called the situation a "living hell" for all Yemeni children, noting the death of a child whose emaciated body gained attention on the front page of the New York Times last week.

"Unfortunately, Amal is not the only Yemeni child suffering that fate," he said in a speech delivered in Amman. "30,000 children in Yemen die every single year of malnutrition as one of the most important underlying causes. There is not one Amal — there are many thousands of Amals."

The Associated Press had photographed the girl, seven-year-old Amal Hussein — whose name means "hope" in Arabic — earlier in October. She suffered severe malnutrition and suspected tuberculosis. Medics say her death was the result of insufficient medical care as supplies dwindle and many people like Amal live far from treatment centers.