Harrowing images show blood-soaked children injured in a Russian airstrike that killed 18 people — including two kids — in an apartment building Tuesday, according to Ukraine’s government.

The distressing images were shared as Ukraine also accused invading forces of violating a cease-fire and attacking an evacuation route — as more than 2 million people have already fled the war-torn nation.

NATO Secretary-General Jens Stoltenberg confirmed there were “very creditable reports of civilians coming under fire as they try to evacuate,” calling it “totally unacceptable” and amounting to “a war crime.”

One image showed a tiny child caked in blood and dust, with bloodied bandages wrapped around the head. Other images appeared to show some of the almost two dozen killed in the attack in Sumy, the first major city that was starting to be evacuated Tuesday.

“Last night Russian pilots committed another crime against humanity in Sumy,” Ukraine’s government said.

“They dropped 500-kilogram [1,100-pound] bombs on residential buildings.

Get the latestupdatesin the Russia-Ukraine conflict with The Post’s live coverage.

On Telegram, the government said another city in the region, Okhtyrka, was also attacked.

“The enemy intensifies the bombardment of urban areas, destroying and damaging residential buildings,” the government shared, saying enemy troops were targeting civilians “to bombard cities into submission.”

The latest bloodshed in Sumy came as Ukrainians boarded buses to flee the besieged eastern city Tuesday, the first evacuation from a Ukrainian city through a humanitarian corridor agreed upon with Russia after several failed attempts to get residents to safety in recent days.

Residents were also leaving the town of Irpin, a front-line Kyiv suburb where women and children were killed in a brutal bombardment Sunday.

In one of the most devastated cities, Mariupol, an estimated 200,000 people — nearly half the population of 430,000 — hoped to flee.

However, the foreign ministry on Tuesday accused Russian forces of still striking one of the agreed-upon safe havens.

“Ceasefire violated! Russian forces are now shelling the humanitarian corridor from Zaporizhzhia to Mariupol,” the department insisted.

The attacks came as “8 trucks + 30 buses” were “ready to deliver humanitarian aid to Mariupol and to evac civilians to Zaporizhzhia. 

“Pressure on Russia MUST step up to make it uphold its commitments,” the ministry tweeted.

“The invaders did not let children, women, elderly people out of the city,” Ukraine’s Joint Forces Operation claimed in a Facebook post, calling it “the genocide of the people of Ukraine.”

Foreign Minister Dmytro Kuleba said it left “300k civilians hostage in Mariupol.”

“One child died of dehydration (!) yesterday! War crimes are part of Russia’s deliberate strategy. I urge all states to publicly demand: RUSSIA, LET PEOPLE GO!” he tweeted early Tuesday.

The evacuations came amid an unprecedented refugee crisis, with the fastest exodus Europe has seen since World War II, according to the United Nations.

“Today the outflow of refugees from Ukraine reaches two million people. Two million,” Filippo Grandi, the UN High Commissioner for Refugees, wrote on Twitter.

The Russian onslaught — now well into its second week — has trapped people inside cities that are running low on food, water and medicine.

While Russian troops have made significant advances in some areas, Ukrainian soldiers and volunteers have so far fortified the capital, Kyiv, with hundreds of checkpoints and barricades designed to thwart a takeover. 

A steady rain of shells and rockets fell on other population centers, including the Kyiv suburb of Bucha, where the mayor reported heavy artillery fire.

“We can’t even gather up the bodies because the shelling from heavy weapons doesn’t stop day or night,” Mayor Anatol Fedoruk said. “Dogs are pulling apart the bodies on the city streets. It’s a nightmare.”

Russian forces also continued their offensive in Mykolaiv, opening fire on the Black Sea shipbuilding center of a half-million people, according to Ukraine’s military. Rescuers said they were putting out fires caused by rocket attacks in residential areas.

Ukrainian defense forces were also involved in operations in the northern city of Chernihiv, the general staff said.

However, Ukrainian officials have repeatedly insisted that Russian troops are demoralized at their lack of success despite their clear advantage.

Ukrainian President Volodymyr Zelensky told ABC News that “for one soldier of Ukraine, we have 10 Russian soldiers, and for one Ukrainian tank, we have 50 Russian tanks.”

Still, he vowed that even if Russian forces “come into all our cities,” they will be met with an insurgency.

With Post wires