Megan Specia

NEW YORK - Nearly three weeks after a Saudi-led coalition blockaded Yemen’s airports and seaports, cutting off much of the country from desperately needed aid, shipments have begun re-entering ports held by Houthi rebels.

The blockade had left millions of people without reliable access to medicine and exacerbated a food crisis that has left much of the country teetering on the brink of famine.

On Sunday, the key seaport of Hodeida received a shipment of flour, Reuters reported, and a day earlier aid planes were allowed to land at the main airport in Sanaa, the capital.

Humanitarian groups have warned that the arrival of lifesaving supplies should not be misinterpreted as an end to the pressing crisis, but instead as the first step in re-establishing a consistent flow of food and medicine to a country with millions of civilians in need.

“We are very grateful for what we could achieve yesterday,” Geert Cappelaere, the regional director for UNICEF, said in a briefing on Sunday in Jordan. “However, this is not enough. Much, much more is needed.”

“Far more humanitarian supplies are needed today,” he said. “Yesterday’s success cannot be a one-off.”

UNICEF delivered 1.9 million doses of vaccines to Sanaa on Saturday, and Cappelaere said the next critical step was to get them to those who need them.

“Getting the supplies is one part,” he said. “Ensuring that the supplies — whatever they are — are reaching every single vulnerable girl and boy throughout Yemen is another challenge.”

The vaccine campaign aims to immunise children against diseases like whooping cough, tuberculosis, pneumonia, meningitis and diphtheria.

Concerns were raised this month when diphtheria, a potentially deadly disease that is under control in much of the world, made a resurgence in Yemen, affecting at least 120 people. The World Health Organization said diphtheria vaccines were among the supplies that had earlier been blocked.

A cholera epidemic, which had been waning after ravaging the country earlier this year, had also threatened to re-emerge after shipments of chlorine tablets used to sanitise water were blocked from arrival. Several cities were cut off from supplies of fuel for pumping in fresh water and processing sewage during the blockade, which the International Committee of the Red Cross said was putting 2.5 million people at risk of waterborne disease.

The Saudi-led coalition began the blockade of sea, air and land ports on Nov. 6 after it said a missile fired by Houthi rebels from within Yemen was intercepted near Riyadh, the Saudi capital. The blockade was later loosened, but until this weekend had kept key Houthi-held ports sealed. The Saudi coalition has been fighting the rebel group since 2015.

Since then, the war has ravaged Yemen’s health care sector, brought about the largest single-year outbreak of cholera ever recorded, killed or wounded thousands of civilians targeted by airstrikes and left 17 million people without reliable access to food.