Four out of five Yemenis now need aid

After a visit to the country in August, the head of the International Committee of the Red Cross (ICRC), Peter Maurer, declared: "Yemen after five months looks like Syria after five years."

The conflict has reached 21 out of 22 of Yemen's provinces and shows no sign of ending. More than 2.51 million people have been displaced internally - more than four times the number recorded at the beginning of 2015. An additional 121,000 people have fled the country.

An estimated 14.4 million are considered food insecure and 7.6 million severely food insecure, according to the WFP.

Scale of humanitarian crisis in Yemen (November 2015)

An estimated 3 million people now require treatment or preventive services for malnutrition. About 2 million are currently acutely malnourished, including 1.3 million children - 320,000 of whom are suffering from severe acute malnutrition.

Yemen usually imports more than 90% of its food. The naval embargo and fighting around the port of Aden have stopped all but a fraction of imports getting through, causing severe shortages of food and price rises. A lack of fuel, coupled with insecurity and damage to markets and roads, have also prevented supplies from being distributed.

Ten of Yemen's 22 provinces provinces have been classified by the WFP at the "emergency" level for food security - one step below "famine".

Internally displaced people in Yemen (November 2015)

The restrictions on imports of fuel - essential for maintaining the water supply - combined with damage to pumps and sewage treatment facilities, also mean that 19.3 million people now lack access to safe drinking water or sanitation.

People have been forced to rely on untreated water supplies and unprotected wells, placing them at risk of life-threatening illnesses such as diarrhoea and cholera.

Those affected, however, will struggle to get medical help. An estimated 14.1 million people across Yemen lack access to basic healthcare, with almost 600 health facilities having stopped functioning due to conflict-related damage or lack of fuel, staff and supplies, according to the UN.

The World Health Organisation (WHO) has warned that medicines for many chronic diseases are no longer available and pregnant women may soon face dramatically increased risks of death during childbirth. Outbreaks of deadly communicable diseases have also been reported.