U.N. officials paint a bleak picture as civilian casualties top 13,000.

As Ukraine celebrated its Independence Day, six months after being invaded by Russia, senior U.N. officials on Wednesday offered a bleak assessment of the situation in the war-battered country.

Ukraine’s vulnerability was called into sharp relief when President Volodymyr Zelensky, addressing the U.N. Security Council on Wednesday, announced during the session that a railway station in eastern Ukraine had been targeted in a Russian missile attack. Later, he said the attack had killed at least 22 people and injured 50.

“There is no such war crime that the Russian occupiers have not yet committed on the territory of Ukraine,” Mr. Zelensky told the Security Council via a video connection. “If Russia is not stopped now in Ukraine, if it’s not stopped by the victory of Ukraine then all these Russian murderers will probably end up in other countries.”

Speaking before Mr. Zelensky informed the Council about the railway attack, António Guterres, the secretary general of the U.N., told the Council that the six-month point of the war was a “tragic milestone” in a conflict in which thousands of civilians, including hundreds of children, had been killed and injured and millions of Ukrainians had been displaced.

“The world has seen grave violations of international human rights law and international humanitarian law committed with little to no accountability,” Mr. Guterres said.

Rosemary DiCarlo, the U.N.’s chief for political and peacemaking affairs, gave a stark update on the humanitarian crisis in Ukraine. Ms. DiCarlo said that, in the past six months, the U.N. had recorded 13,560 civilian casualties there, including 5,614 people killed and 7,946 injured. The true numbers of civilians killed and injured are likely to be far larger. Ukraine itself has reported that tens of thousands have died in Russian bombardments and other attacks.

At least 17.7 million people, or 40 percent of the Ukrainian population, need humanitarian assistance and protection, including 3.3 million children, she said.

Mr. DiCarlo warned that, as winter approaches, the destruction caused by war, combined with the lack of access to fuel or electricity because of to damaged infrastructure, “could become a matter of life or death.”

Vasily Nebenzya, Russia’s ambassador to the U.N., said the session on Wednesday had ignored events on the ground, engaged in Russia-bashing and demonstrated “the unfailing support of western countries for any actions of the Kyiv regime.”