Arab foreign ministers will gather in London on Tuesday to discuss the devastating humanitarian crisis in Yemen amid growing calls for increased aid access to the country.

The Saudi-led coalition battling Houthi rebels eased its blockade for humanitarian flights and ships after closing all land, sea and air access to Yemen earlier this month in a bid to stem the flow of weapons from Iran.

The UN and Britain have called for more ports and airports to be opened to alleviate what UK Foreign Secretary Boris Johnson described as “the world’s worst humanitarian crisis”.

"The people who are suffering most from this conflict are the people of Yemen," the Foreign Secretary said.

A UN aid ship carrying enough food to feed 1.8m people in northern Yemen for a month was allowed to dock at a rebel-held port on Monday while planes carrying medical supplies were allowed to land in the capital Sanaa on Saturday.

"I welcome the steps taken towards reopening the ports of Hodeidah and Salif and the resumption of UN flights to Sanaa airport,” Johnson said.

“The UK will continue to press for humanitarian and commercial access to be restored to all ports, so that the already dire humanitarian situation does not deteriorate further.”

"We will also be taking forward the UN-led diplomatic process, as well as reviewing the security situation including the recent attempted ballistic missile strike."

The Saudi-led coaltion imposed the blockade on Yemen after a missile was launched at Riyadh International Airport from rebel-controlled territory.

Foreign ministers from Saudi Arabia, the United Arab Emirates and Oman will attend the meeting in London, along with US officials.

More than 20 million people in Yemen are in need of urgent humanitarian assistance. Eleven million of those are children and 400,000 are affected by severe acute malnutrition.