Image copyright AFP/Getty Images Image caption In Yemen, eleven million children are in need of urgent humanitarian assistance

The United Nations has appealed for a record $22.5bn (£17bn) in humanitarian aid for 2018.

The global aid appeal aims to raise funds to help 91 million of the world's most vulnerable people, out of 136 million in need, a UN statement said.

More than $10bn is needed to address the humanitarian crises in Syria and Yemen alone, it added.

The UN also said needs are rising substantially in a number of African countries.

Driven by conflicts in Africa and the Middle East, the number of people in need of humanitarian aid has increased by more than 5%, according to UN co-ordinator Mark Lowcock.

The targeted fund is a 1% increase on the amount requested last year. By the end of November, the agency had raised nearly $13bn - which the UN says is record levels of funding.

More than a third of the fund requested is to address the needs created by the devastating civil war in Syria: $3.5bn to provide humanitarian aid inside the war-ravaged country and $4.2bn to help the 5.4m registered Syrian refugees in neighbouring countries.

In Yemen, which is facing the world's worst humanitarian crisis, the UN says $2.5bn is needed to assist those most desperately in need.

The UN has acknowledged they aim to cover the needs of only half of the 20 million people in Yemen who are in need of urgent humanitarian assistance. Eleven million of those are children and 400,000 are affected by severe acute malnutrition.

Each of Congo, Ethiopia, Nigeria, Somalia, South Sudan and Sudan are in need of more than a billion dollars of aid to assist the most vulnerable.

The UN statement also said that in some other countries, including Afghanistan, Ethiopia, Iraq, Mali, and Ukraine, humanitarian needs have declined.