On Friday, Russian forces seized a massive nuclear power plant in southeastern Ukraine, extending their siege of cities along the country’s southern coast, including Mariupol, whose mayor warned the city was “on the verge of a humanitarian catastrophe.”

A city council member in Kherson, a regional capital and the first major city to fall to Kremlin forces, said Russian equipment and soldiers were “absolutely everywhere.”

In Kharkiv, Ukraine’s second-largest city, Russian troops have fired cluster munitions into at least three residential neighborhoods, according to a report released Friday by Human Rights Watch.

The number of casualties caused by fighting has been impossible to verify as the violence quickly spreads across Ukraine. The UN human rights office reported on Friday that at least 331 civilians had been killed, while Ukraine’s emergency services reported that the number of civilian fatalities was much higher, at over 2,000. According to a United Nations statement, the majority of the casualties were caused “by the use of explosive weapons with a wide impact area, such as shelling from heavy artillery and multi-launch rocket systems, as well as missile and airstrikes.” Russia has confirmed the deaths of approximately 500 of its troops, while Ukrainian officials claim that up to 10,000 Russian soldiers have been killed or captured.

Russia’s seizure of Europe’s largest nuclear power plant, Zaporizhzhia, followed shelling that set part of the complex on fire, raising fears across Europe of a catastrophic meltdown. The United Nations nuclear watchdog said the fire had not affected “critical” equipment, and Ukraine’s regulator said there had been no change in radiation levels in the area. Jennifer Granholm, the United States’ Energy Secretary, tweeted that the Energy Department had also seen no elevated radiation readings.

Meanwhile, Kherson faces a “global catastrophe” if a humanitarian corridor is not opened soon to allow civilians to be evacuated and food and medicine to be delivered, according to the city council secretary.

With the conflict in its second week and Russia sending nearly all of its military force into neighboring Ukraine, satellite images are providing glimpses of the scale of the invading force, as well as the devastation caused by the fighting. Maxar Technologies’ analysis of satellite imagery shows bridges and roads damaged and homes destroyed in towns and cities across the country.

The images show damaged roads, bridges, and homes in Chernihiv, a strategic northern city on a highway that connects Ukraine’s border with Belarus to Kyiv and has seen a fierce battle in recent days. Some of the factories appear to have been destroyed. In a Facebook post on Friday, Chernihiv’s regional authority said that strikes killed 47 people, including nine women.

The images also show a long Russian armored column north of Kyiv, the capital. This massive convoy has remained stalled due to logistical difficulties and fierce resistance from Ukrainian forces, according to Western officials.

The column of combat and logistics vehicles “is now likely supporting attacks directly into the city from positions that Russian forces maintain on Kyiv’s northwestern outskirts,” a senior western intelligence official said Thursday, adding that Russian forces were more likely “to prioritize encircling the city in the coming days rather than a direct assault on it.”

Concerns about the fate of Ukraine’s cities have grown as evidence mounts that Russian forces are targeting urban areas with indiscriminate weapons. Human Rights Watch stated in its report on Friday that it had documented the use of cluster munitions based on two witness interviews and the analysis of 40 videos and images. According to the group, some of these sources show “explosion signatures and rocket remnants” consistent with the delivery of cluster munitions from 9M55K Smerch rockets.

Human Rights Watch claimed that Russia may have committed a war crime by using cluster munitions due to their indiscriminate nature (they scatter small bomblets over a wide area that could explode even after the fighting is over, endangering civilian safety).