The UN secretary-general on Tuesday urged warring sides in Yemen for a political settlement.
Speaking at a high-level pledging conference in Geneva held to discuss the crisis in Yemen, Antonio Guterres asked donor countries to provide nearly $3 billion in aid to the country where humanitarian access is restricted in 90 percent of districts.
"Yemen is the world's worst humanitarian crisis. As the conflict enters its fourth year, more than 22 million people-three-quarters of the population-need humanitarian aid and protection.
"We must see action to end the conflict...There are no humanitarian solutions to humanitarian crises. A negotiated political settlement through inclusive intra-Yemeni dialogue is the only solution. I urge all parties to engage with my new Special Envoy, Martin Griffiths, without delay," Guterres said.
The 2018 Humanitarian Response Plan for Yemen requires $2.96 billion to reach more than 13 million people across the country.
"Some 18 million people are food insecure; one million more than when we convened last year. A horrifying 8.4 million of these people do not know how they will obtain their next meal," Guterres said.
"Yemen's situation today is catastrophic. But with international support, we can and must prevent this country from becoming a long-term tragedy," he said.
Noting that last year's donor conference raised $1.1 billion for humanitarian action in Yemen, Guterres said Saudi Arabia and the United Arab Emirates have provided $930 million and pledged to secure an additional $500 million from the region while other donors have contributed some $293 million so far which means 40 per cent of the requirements have been provided for the year.
"The scale of suffering that we see in Yemen requires rapid, full funding for the 2018 response plan," said Guterres, adding: "The plan is prioritized so that every dollar goes where it is urgently needed. I urge all to do whatever is possible."
Noting that all ports must remain open to humanitarian and commercial cargo, the medicines, food and the fuel, Guterres said: "Humanitarians must be able to reach the people who need help the most, without conditions."
"Humanitarian agencies and their partners need full and unconditional access at all times. But humanitarian agencies report access constraints in 90 percent of districts in Yemen," Guterres said.
Yemen has remained dogged by conflict since 2014, when the Houthi militia overran much of the country, including the capital Sanaa.
In 2015, Saudi Arabia and its Arab allies -- who accuse the Houthis of serving as a proxy force for Iran -- launched a wide-ranging military campaign aimed at rolling back Houthi gains and shoring up Yemen's Saudi-backed government.
Several children were killed in an attack on Monday in the coastal city of Hodeida in western Yemen and many children are reported missing, UN children's fund, UNICEF said on Tuesday.
"This is one of the deadliest attacks on children since the conflict in Yemen escalated in March 2015," UNICEF said in a statement.
