Four planes from aid groups arrived Saturday in Yemeni capital Sanaa marking an end to a blockade by a Saudi-led alliance of the rebel-held airport, a local official said.

A flight carrying humanitarian aid worker landed in Sanaa, the first after a nearly three week blockade imposed by the Saudi-led military coalition, an official of the U.N.'s World Food Programme (WFP) said.

An estimated 17 millions of Yemen's 27 million people are suffering from food insecurity as a civil war has dragged on for three years.

Two of the aid aircraft belong to the United Nations, and one each to the UN Children's Fund (UNICEF) and the International Committee of the Red Cross, the official told dpa.

The UNICEF plane was loaded with urgent relief supplies, while the three others carried aid workers, the official added.

The UN Children's Fund said Saturday's flight was carrying more than 15 tonnes, or 1.9 million doses, of vaccine for diphtheria, tetanus and other preventable diseases.

The World Health Organization confirmed earlier this week that diphtheria was spreading as children went unvaccinated and doctors in Hodeida reported three deaths.

The Saudi-led coalition is fighting the Iran-backed Houthi rebels, who seized control of Sana'a in late 2014 and have since taken over other parts of the impoverished country.

The coalition closed all airports and ports in Yemen on November 5, a day after the Houthis fired a ballistic missile at Saudi capital Riyadh.

The Sunni alliance said the closure was aimed at stopping the flow of Iranian arms to the Shiite Houthis.

On Wednesday, the coalition said it would allow humanitarian aid into Yemen through Sana'a airport and the western port of Hodeida.

The coalition fighting the armed Houthi movement in Yemen said on Wednesday it would allow aid in through the Red Sea ports of Hodeidah and Salif, as well as U.N. flights to Sanaa, but there has been no confirmation of any aid deliveries yet.