(CNN)Nearly one in five children live in areas affected by armed conflict and war, according to a new report published by the charity Save the Children.
Almost 1 in 5 children live in conflict zones, Save the Children says
Some 420 million children were living in conflict-affected areas in 2017, marking the largest number of children living in areas affected by armed conflict than at any time in the past 20 years, it said.
The report defined affected children as those living within 50 kilometers (about 30 miles) of where one or more conflict events took place in a year within a country's borders.
Children were hit hardest by conflict in Afghanistan, Yemen, South Sudan, the Central African Republic, the Democratic Republic of Congo, Syria, Iraq, Mali, Nigeria and Somalia in 2017, according to the report, "Stop the War on Children: Protecting Children in 21st Century Conflict," with research carried out by the Peace Research Institute Oslo.
The report said one reason 2017 saw an increase in children living in conflict-affected areas is that modern warfare has changed the lines of engagement, with fighting in urban areas among civilian populations more common and international rules disregarded.
Grave violations against children -- which include being killed, maimed, recruited or abducted by armed groups, sexual violence, attacks on schools and denial of humanitarian aid -- rose globally from just less than 10,000 in 2010 to 25,000 in 2017, the highest number ever recorded, United Nations data analyzed in the report show.
Children were specifically targeted in many of those cases, the report said.
The report's findings demonstrate that "the way today's wars are fought is causing even more suffering for children," said Carolyn Miles, president and CEO of Save the Children.
"Our analysis clearly shows the situation is getting worse for children and the world is allowing this travesty to happen. Every day, children come under attack because armed groups and military forces disregard international laws and treaties. From the use of chemical weapons to rape as a weapon of war, war crimes are being committed with impunity," she said.
Save the Children included more than 20 recommendations on how best to safeguard children against violations of humanitarian law and human rights in the report, and it is calling for an independent body to investigate such violations.
"When the rules of war are broken, the international community must be clear that this will not be tolerated and hold perpetrators to account," Miles said. "And for the children whose lives are wrecked by conflict, we must do all we can to protect them from further harm and help rebuild their futures."