Millions of people will die in Yemen, in what will be the world's worst famine crisis in decades, unless a Saudi-led military coalition ends a devastating blockade and allows aid into the country, the United Nations has warned.

The Saudi-led alliance fighting Yemen's Houthi rebels tightened its air, land and sea blockade of the country after a ballistic missile was fired on Saturday towards the Saudi capital, Riyadh.

Since then, the country's already inflated food and fuel prices have skyrocketed, while flights delivering much-needed humanitarian aid have been prevented from landing.

After briefing the UN Security Council on Wednesday, Mark Lowcock, the UN's humanitarian chief, said the move will worsen a "catastrophic" humanitarian crisis that has pushed millions to the brink of famine and has caused a mass cholera epidemic.

"I have told the Council that unless those measures are lifted ... there will be a famine in Yemen," Lowcock, who visited Yemen late in October, told reporters on Wednesday.

"It will not be like the famine that we saw in South Sudan earlier in the year, where tens of thousands of people were affected. It will not be like the famine which cost 250,000 people their lives in Somalia in 2011," he added.

"It will be the largest famine the world has seen in many decades, with millions of victims."

'Guarded response'

Despite Lowcock's stark warning, the Security Council, which strongly condemned the firing of the missile by the Houthi rebels, announced no immediate action over the blockade.

Italian Ambassador Sebastiano Cardi, who holds the council's presidency, expressed concern about the "dire humanitarian situation in Yemen" and stressed "the importance of keeping all Yemen's ports and airports functioning," added Cardi.

Al Jazeera's James Bays, reporting from the UN headquarters in New York, said the Council's response "seemed very guarded".

He said the comments by Lowcock, who visited Yemen late last month, had brought some of the "reality from Yemen to the Security Council, but for now, they've responded with very carefully chosen words rather than any concrete action".

Kristine Beckerle, Yemen researcher at Human Rights Watch, said it was "far past time" the members of the UN Security Council "made it very clear" to Yemen's warring sides that there will be "concrete consequences" in cases of obstruction to humanitarian assistance.

"The Council already has a mechanism for sanctioning people in Yemen who are committing gross violations," she told Al Jazeera.

Beckerle said government officials in countries such as the US, UK and France are typically "issuing broad recitations of concern", without, however, acting upon it.

"It's not enough for the US or the UK to say we are worried about famine in Yemen.

"At this point, it's up to the Security Council members, and particularly those allied with Saudi Arabia, to be using all the leverage at their disposal to be pushing these people to actually make changes to the ways in which they are fighting this war and certainly for them to stop impending access to aid."

Yemen has been devastated by more than two and a half years of war after Houthi rebels, believed to be backed by Iran, captured the capital, Sanaa, and overthrew President Abd-Rabbu Mansour Hadi's government.

A Saudi-led coalition was formed in 2015 to fight the Houthi rebels and army troops allied with them.

According to the UN, the conflict has killed more than 10,000 people and left over seven million in need of food assistance.

Millions of others do not have adequate access to health, water and sanitation services.

The country has also been hit by a cholera outbreak, with some 900,000 suspected cases since April.

PHOTO CAPTION

Parents of malnourished girl Jamila Ali Abdu, 7, are seen as she lies on a hospital bed before she died in the Red Sea port city of Hodeidah, Yemen May 2, 2017. REUTERS

Al-Jazeera