Russian forces executed Ukrainians as they tried to surrender: US officials
A Ukranian serviceman walks in the village of Mala Rogan. (Aris Messinis AFP)

U.S. officials said they have reliable information that Russian military forces executed Ukrainians who were trying to surrender.

The Ukrainians were killed "execution-style" with their hands bound, according to ambassador-at-large for global justice Beth Van Schaack, who said the U.S. had received credible reports and photos from the incident, reported USA Today.

“These images and reports suggest that atrocities are not the result of rogue units or individuals; they, rather, reveal a deeply disturbing pattern of systematic abuse across all areas where Russia’s forces are engaged,” Van Schaack said Wednesday at a United Nations meeting.

Ukrainian president Volodymyr Zelenskyy gave the U.N. Security Council detailed reports about killing, rape and torture after visiting Bucha, where he said Russian forces "killed entire families," crushed civilians with tanks, maimed civilians and slashed throats.

Investigators and volunteers have also documented a campaign of brutality against civilians in towns near Kyiv as Russian troops withdrew from the area.

In Mariupol, civilians face "mortal danger," according to reports. Roughly 100,000 civilians are at risk.

U.S. officials have also warned the war threatens to expand into neighboring countries, including Moldova, a small nearby country. Earlier this week, Russia cut off gas shipments to Poland and Bulgaria, NATO member states.

The U.S. has increased arms shipments to Ukraine. Germany, once reticent about sending heavy weaponry, recently agreed to send anti-aircraft tanks.