Yemen’s rebels continued their weekslong blockade of a district in the central province of Marib, cutting off humanitarian aid and halting movement of its 37,000 people, officials and U.N. aid workers said Sunday.

The Iran-backed Houthi rebels have advanced in the district of Abdiya south of the city of Marib in recent weeks, forcing troops of the internationally recognized government to retreat, military officials from both sides said.

The Houthis “are committing genocide” in Abdiya, preventing food, medicine and other basic needs from reaching the district, said Marib provincial Gov. Sheikh Sultan al-Aradah.

The attack on Abdiya is part of the Houthis’ offensive to capture the government-held city of Marib, which the rebels have been trying to seize for years. They intensified their offensive in February, apparently emboldened by a decision by President Joe Biden’s administration to end U.S. support to the Saudi-led coalition. However, they've faced stiff resistance from government and tribal forces aided by the coalition.

Yemen has been engulfed in a civil war since 2014, when the Houthis captured the capital, Sanaa, and forced President Abed Rabbo Mansour Hadi and his internationally recognized government to flee to the south, and then later to Saudi Arabia. A Saudi-led coalition entered the war the next year to try restore the government to power. The war has deteriorated largely into a stalemate and spawned the world’s worst humanitarian crisis.

Thousands of fighters, mostly Houthis, have been killed in clashes and airstrikes around the city of Marib. The Houthis usually attack with waves of fighters charging government lines, thereby becoming easy targets in the open desert for coalition warplanes.

Children recruited by the Houthis are among those killed in the fighting. Placards with photos of child soldiers are commonplace on the streets in rebel-held areas including the capital, Sanaa.