Russia's attacks on Ukraine's civilian infrastructure, including energy facilities, have been described as possible war crimes by the office of the United Nations High Commissioner for Human Rights and Amnesty International.
On Friday, Russia launched dozens of missiles across Ukraine knocking out electricity in its second biggest city, hitting critical infrastructure in the south and causing explosions in the capital Kyiv, Ukrainian officials said.
Eight people were also killed and 23 injured by Ukrainian shelling in the Russian-controlled Luhansk region of Ukraine, the Russian-installed administrator of the region said.
Reuters could not immediately verify the battlefield reports.
What does international law say?
The Geneva conventions and additional protocols shaped by international courts say that parties involved in a military conflict must distinguish between "civilian objects and military objectives" and that attacks on civilian objects are forbidden.
This prohibition is also codified in the Rome Statute of the International Criminal Court (ICC), which earlier this year opened an investigation into possible war crimes in Ukraine.
That seems clear-cut, but some infrastructure owned and used by civilians can also be a military objective. Military objectives are defined as "those objects which by their nature, location, purpose or use make an effective contribution to military action" and whose destruction or capture "offers a definite military advantage."
Is energy infrastructure military or civilian?
Power infrastructure has long been considered a valid military objective as long as it supports an enemy army's activities, even if the system also supports the civilian population, writes military law expert Michael Schmitt in the Articles of War blog run by the Lieber Institute for Law & Warfare at the United States Military Academy West Point.
As Russia's strikes on the power infrastructure have intensified, it seems increasingly unlikely that its armed forces can name a "definite" military benefit for each attack.
"Simply put, Russian forces are almost certainly striking many targets that do not qualify as military objectives," Schmitt argues.
Russia says it attacks military targets including energy infrastructure.
How are military needs balanced against civilian?
Even if some of the targets could be considered military objectives, that is not the end of the story, says Katharine Fortin, associate professor of international law at Utrecht University.
The military must consider whether the damage and loss incurred by civilians in such attacks are excessive compared to the concrete and direct military advantage, she said.
"In this instance, the incidental loss of life and injury to civilians that can be expected seems very large given that power outages are making it impossible for surgeons to carry on their work, affecting people's access to healthcare, and creating conditions in which vulnerable people are dying due to the cold or hunger," she told Reuters.
How do war crime prosecutors consider the current attacks?
Nigel Povoas, lead prosecutor for a team of international experts assisting Kyiv war crimes investigators, told Reuters that Russian attacks in the past two months have "focused on eliminating infrastructure crucial to the means of civilian survival such as heat, water, power and medical facilities."
Both Schmitt and Povoas say the scale and the intensity of the attacks can additionally amount to them being considered as "acts or threats of violence the primary purpose of which is to spread terror among the civilian population."
This is forbidden under international humanitarian law and was confirmed as a war crime by rulings of the U.N. tribunal for the former Yugoslavia relating to the siege of Sarajevo.