Up to two million people living near the front line in eastern Ukraine risk being displaced if fighting resumes, the Norwegian Refugee Council warned on Thursday.
"The lives and safety of millions of people in eastern Ukraine are on hold while we wait for a political breakthrough to break the deadlock," the NGO's secretary-general Jan Egeland said in a statement.
"We should not underestimate the human suffering that would result from a renewed conflict, which would increase the number of civilian casualties, cause massive displacement and increase humanitarian needs," he said.
Since late 2021, the West has accused Russia of massing hundreds of thousands of troops on the Ukrainian border in preparation for a military operation against Kyiv, which Moscow denies.
Eastern Ukraine has already been in the midst of a war between Kyiv and pro-Russian separatists since 2014, a conflict that broke out after Moscow annexed Ukraine's Crimea.
The war, which has killed more than 13,000 people, has sharply decreased in intensity since peace agreements in 2015, but the political settlement of the conflict has been mired in disagreements since then. Along the frontline, gunfire continues to claim lives regularly.
According to the Norwegian Refugee Council, more than 850,000 people have already been displaced in Ukraine due to the fighting.
An active resumption of the conflict could, according to the NGO, undo the "significant progress" of recent years in the living conditions of people in eastern Ukraine.
The number of people depending on humanitarian aid there has fallen from 5 million in 2015 to 3 million today, according to the Norwegian Refugee Council.