The UK will send £200m in aid to help developing nations battle coronavirus.
The money will mean more help for refugee camps - including new hand-washing stations.
International Development Secretary Anne-Marie Trevelyan said boosting fragile health systems overseas would help prevent a "second wave" of infections hitting the UK.
The latest donation brings Britain's total contribution to the global effort to halt the pandemic to £744m.
It makes the UK one of the biggest donors to the worldwide fight against the virus, according to the Department for International Development (Dfid).
Britain's funding will help install new hand-washing stations and isolation and treatment centres in refugee camps, and increase access to clean water for those living in areas of armed conflict, Dfid confirmed.
There will also be extra support for Yemen, where only about 50% of health facilities are operational, due to the country's ongoing civil war.
The UN has already warned richer countries that Covid-19 will "circle back around the world" in a second wave if they do not help poorer nations cope with the pandemic.
Of the £200m in funding, £130m will go to United Nations agencies, including £65m for the World Health Organization (WHO), which is co-ordinating the global response to the pandemic.
Another £50m will boost the Red Cross in difficult to reach areas such as those affected by armed conflict, and a final £20m will help non-government organisations, including UK charities.
Ms Trevelyan said: "While our brilliant doctors and nurses fight coronavirus at home, we're deploying British expertise and funding around the world to prevent a second deadly wave reaching the UK
"Coronavirus does not respect country borders so our ability to protect the British public will only be effective if we strengthen the healthcare systems of vulnerable developing countries too."
WHO director general Tedros Adhanom Ghebreyesus said: "We are all in this together, which means protecting health around the world will help to protect the health of people in the UK."
The UK has already committed £250m in aid to the Coalition for Epidemic Preparedness Innovations (CEPI) to rapidly develop a coronavirus vaccine, the biggest donation of any country.
The UK's latest donation comes after US President Donald Trump accused the WHO of being "China-centric" in its tackling of the pandemic, and said the US would take "a good look" at its financial contributions to the organisation.
The W.H.O. really blew it. For some reason, funded largely by the United States, yet very China centric. We will be giving that a good look. Fortunately I rejected their advice on keeping our borders open to China early on. Why did they give us such a faulty recommendation?— Donald J. Trump (@realDonaldTrump) April 7, 2020
Dr Tedros later dismissed Mr Trump's comments and called for an end to the politicisation of Covid-19.
The World Bank has already committed £9.4bn in aid for developing fighting the spread of the virus, and has warned that the financial impact of coronavirus will stop almost 24 million people from escaping poverty in East Asia and the Pacific.