UNITED NATIONS (AP) — The United Nations said Monday that the Saudi-led coalition fighting in Yemen has eased restrictions at the main airport and two key ports, allowing the resumption of some humanitarian aid to the conflict-wracked country after a three-week blockade.

U.N. spokesman Stephane Dujarric said three humanitarian flights landed and took off from the capital of Sanaa on Saturday, the first commercial cargo vessel docked in the port of Hodeida on Sunday, and a U.N.-chartered vessel docked at the port in Salif on Monday.

Despite the resumption, he warned that rapidly dwindling fuel stocks and the dire humanitarian situation are pushing at least 7 million people toward famine.

Dujarric said the commercial ship carried 5,500 metric tons of wheat flour and the U.N.-chartered vessel carried 25,000 metric tons of bulk wheat.

But he stressed that "it is important that there is unimpeded access for both humanitarian and commercial cargo to enter Hodeida and Salif ports, including those carrying fuel."

"Fuel is urgently required to operate generators for hospitals, water well pumps and sanitation units and to facilitate the trucking of drinking water and staple food" to some 21 million Yemenis who need humanitarian assistance, he said.

Dujarric said one of the flights Saturday delivered 1.9 million doses of diphtheria vaccines, enough to protect 600,000 children against whooping cough, tuberculosis, pneumonia and meningitis.

"These vaccines will help to contain the current outbreak of diphtheria, which since August has seen more than 170 suspected cases and at least 14 deaths recorded in Ibb governorate," he said.

Earlier in the day, the Nobel Women's Initiative, a group of Nobel peace laureates, had urged the Saudi-led coalition fighting Shiite rebels in Yemen to end the blockade on the Arab world's poorest country, citing the hardships it has caused.

In a statement, the group said the blockade "rendered access to humanitarian assistance impossible for the people of Yemen" and "denies millions of vulnerable and innocent civilians access to food, fuel and medical supplies."

The letter was signed by Mairead Maguire of Northern Ireland, Rigoberta Menchu Tum of Guatemala, Jody Williams of the United States, Shirin Ebadi of Iran, Leymah Gbowee of Liberia, and Tawakkol Karman of Yemen.

The Saudi-led coalition went to war against the rebels, known as Houthis, in March 2015 on behalf of Yemen's internationally recognized government. But the coalition has made little progress, and the rebels still control much of northern Yemen, including Sanaa.

The U.S.-backed coalition tightened a land, sea and air blockade Nov. 6 after a missile attack by rebels on the Saudi capital of Riyadh. Saudi Arabia said Monday that the coalition would lift the blockade.

Over the past two years, the war in Yemen has killed more than 10,000 people and left over 3 million displaced amid the coalition's air campaign.

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Associated Press writer Brian Rohan reported this storyifrom Cairo and AP writer Edith M. Lederer reported at the United Nations.