Diarrhoea and other diseases related to poor sanitation are bigger killers of children in areas of conflict than violence and war itself, a report has found, highlighting the need for improved infrastructure as a way of helping civilian populations afflicted by warfare.

Children under five are more than 20 times more likely to die from diarrhoeal diseases than from direct violence, according to Unicef. Henrietta Fore, the organisation’s executive director, said: “The reality is there are more children who die from lack of access to safe water than by bullets.”

Women and children, who tend to be responsible for fetching water, are often unable to reach clean water sources in situations of conflict, while sometimes armed forces deliberately target water supplies and sanitation as weapons of war. Forces can also cut off the power that keeps vital infrastructure such as water pumps working, and conflict prevents maintenance personnel from making repairs.

War also makes it harder for supplies of products needed to purify water or used in sanitation, such as chlorine and other cleaners, to get through to where they are needed.

These factors add up to often neglected disasters that accompany protracted conflicts, with children bearing the brunt, according to a Unicef report, Water Under Fire, published on Friday to coincide with World Water Day. The report examined in detail 16 countries undergoing long civil wars and other conflicts.

Fore called for an end to the deliberate targeting of water infrastructure, including attacks by governments, and for the international community to prioritise water and sanitation in its response to conflicts. “The odds are already stacked against children living through prolonged conflicts, with many unable to reach a safe water source,” she said. “Deliberate attacks on water and sanitation are attacks on vulnerable children. Water is a basic right. It is a necessity for life.”

The report drew on countries including Afghanistan, the Democratic Republic of the Congo, Mali, Somalia, Sudan, Syria and Yemen. Children aged up to 15 were found to be more likely to die from water-related diseases than as a result of direct violence in all the countries studied except for Libya, Iraq and Syria.

Megan Wilson-Jones, a senior policy analyst for health and hygiene at the charity WaterAid, said: “The findings of the report are tragic. Diarrhoea caused by dirty water and a lack of sanitation contributes to the death of a child under five every two minutes.

“Ensuring good water, sanitation and hygiene is essential to the health of children in every setting, including as part of humanitarian emergency responses.”

At least 4 billion people live in water-scarce areas, where for at least part of the year demand outstrips supply, and 844 million lack access to safe water close to home.

Water scarcity is no longer just a problem for developing countries, as climate change, population increases, water wastage and increasing demand from agriculture and industry mean water supplies in large areas of the developed world are also coming under pressure. Earlier this week, the head of the UK’s environment agency warned England would face “the jaws of death”, running out of water within 25 years if nothing were done to halt demand growth and waste.

Unicef’s findings came as a separate report, also focused on World Water Day, showed international businesses are continuing to drain global water supplies, even as they acknowledge the risks and potential negative impacts of doing so. CDP, an organisation focusing on measuring companies’ environmental impacts, looked at some of the world’s 300 biggest publicly listed companies and found roughly one-third are using more water than three years ago.

Cate Lamb, the director of water security at CDP, said more companies must show leadership if the world is not to face a worsening problem. “The world is not on track to meet our global water goal [under the UN’s sustainable development goals] of ensuring access to sustainable water and sanitation for all,” she said.

“The companies reporting to CDP are responsible for a huge proportion of global water use and pollution. While many of their practices and procedures currently contribute to the depletion of freshwater resources, these companies could also hold the key to a water-secure future.”

WaterAid also pointed to the indirect use of water, which many people are unaware of, as key to solving the world’s water and sanitation crises. Although 4 billion people globally live in water-scarce areas, a number expected to rise to 5 billion by the middle of this century, many of these regions effectively export water in the form of agricultural goods from avocados to cotton. High consumption of these goods in buyer countries can lead to worsening problems for people in the exporting countries.