The UK government has pledged £100m to help South Sudan battle a famine which is threatening millions of lives.
The Department for International Development said the new UK support will provide lifesaving food, water and emergency healthcare.
Famine has been declared in two areas of South Sudan following a three-year civil war which has led to a deepening economic crisis.
According to Unicef over 250,000 children are believed to be severely malnourished and at high risk of starvation.
International Development Secretary, Priti Patel, called on the world to "act now to help innocent people".
She said: "In times of crisis, the world looks to Britain not just for our work on the ground, but also for our leadership internationally.
"While we step up our support for emergency food, water and lifesaving care to those in need, our message to the world is clear – we must act now to help innocent people who are starving to death."
In South Sudan the UK's support package will provide:
Food assistance for over 500,000 people
Life-saving nutritional support to more than 27,500 children
Safe drinking water for over 300,000 people
Emergency health services for over 100,000 people
Livelihood support for over 650,000 people
Vaccinations for over 200,000 livestock
Alongside the additional funds for South Sudan, the UK has also pledged £100m in new support for Somalia where there are 360,000 acutely malnourished children.
The money will provide emergency food and safe drinking water to up to one million people and emergency healthcare for 1.7 million.
Over the last three years the UK government has given £500 million to support vulnerable people in South Sudan in need of food, water and medicine.
Up to 400 UK troops will also be deployed this year to support the UN Mission in South Sudan by providing engineering and medical assistance.
Unicef has warned that almost 1.4 million children are at "imminent risk of death" due to famine across four African countries - South Sudan, Nigeria, Yemen and Somalia.