When Russian forces retreated last week from most of Ukraine’s Kharkiv region, they left behind tanks and a howitzer — and disturbing reports of violence. In the village of Zaliznychne, one woman describedburying the bodies of two men killed after they kept lights on past curfew. In other towns, Russian shelling destroyed civilian targets, including schools and hospitals. Officials from the city of Izyum claim at least 1,000 Civilians were killed and 80 percent of the city destroyed during a six-month occupation.

Grisly evidence is emerging. On Thursday, Ukraine’s chief police investigator announced the discovery of a mass burial site near Izyum, containing more than 400 bodies. An Associated Press video showed hundreds of graves lining the forest, marked with numbers and simple wooden crosses. While many of the victims were killed by shelling and airstrikes, some were reportedly found with their necks and hands tied, suggesting the execution of prisoners.

These horrifying allegations follow a sad pattern. From Chechnya to Syria, Russia has a record of waging war with a brutal disregard for human rights and civilian life. In Ukraine, perhaps the most infamous example is what happened in the city of Bucha, near Kyiv: After Russian Troops retreated in late March, more than 450 bodies were found, and the majority of the victims had been tortured, shot or bludgeoned to death. The images spurred global outrage, as did reports of systematic sexual violence and rape.

Since then, evidence has mounted suggesting Russia has committed atrocities. A database from the Associated Press and Frontline has documented 430 “incidents involving potential war crimes” across Ukraine, including attacks on civilians, food and water facilities and medical infrastructure.

In the coming weeks, the world will learn more about what Ukrainian civilians in the Kharkiv area experienced. Towns such as Izyum have been cut off from the internet, phone signals and electricity for months, with little information escaping about conditions and treatment. The Ukrainian government has dispatched investigators and prosecutors to the region to gather evidence, and international investigations will no doubt follow suit. It is imperative reports of violence are quickly and carefully documented. Collecting information in real time — crucial in such situations — will require both resources and coordination.

“Russia leaves death everywhere. And it must be held accountable for it,” Ukrainian President Volodymyr Zelensky said in a video address Thursday night. Every day, Russian President Vladimir Putin’s senseless war in Ukraine claims more lives and causes irreparable suffering. There must be an urgent, thorough investigation into alleged crimes against civilians, followed by sincere efforts to prosecute perpetrators and hold them accountable. Anything less would represent a grave injustice for victims and survivors — and would send an unacceptable signal to Mr. Putin that his troops can commit atrocities with impunity.