With the help of photographs and military documents provided by Yefremov, journalists were able to confirm that at the beginning of the war he was indeed in Ukraine - in the Zaporizhia region, including the city of Melitopol.

He is the highest-ranking officer who agreed to speak openly about the abuse of prisoners by a number of Russian soldiers, notes the BBC.

Yefremov, in particular, talked about the interrogations of Ukrainians brought to their unit in the city of Kamenka in the Zaporizhia Region.

Konstantin Yefremov's unit was entrusted with guarding the "rear headquarters" there.

The colonel was doing the interrogations.

"Once the colonel asked the prisoner, name me the nationalists you know in your regiment, platoon.

And the guy doesn't understand the question, we do, says the marines of the Armed Forces of Ukraine.

For this, the colonel beat him, knocking out several teeth," the man told the BBC.

According to him, the colonel put a gun to the boy's head several times.

"He said that now he would count to three and shoot;

counted, then shot near the head.

At the same time, he continued to ask questions.

The prisoner was shouting, he didn't hear the questions because he was stunned," Yefremov said.

He noted that the interrogations and torture continued for a week: "Every day or night, sometimes twice a day."

The Russian authorities called the need for "demilitarization" and "denazification" of Ukraine the goals of the invasion at the very beginning.

"No one believed that there would be a war"

Konstantin Yefremov, in the rank of senior lieutenant, commanded the demining platoon of the 42nd Motorized Rifle Division stationed in Chechnya.

In this position, he came to the annexed Crimea for training on February 10 last year.

"No one believed that there would be a war.

Everyone believed that there would be exercises.

Even senior officers, I'm sure, didn't know," says the soldier.

He and his unit were ordered to move towards Ukraine on February 27.

On May 27, Yefremov, according to his words, arrived at his military unit in Grozny and wrote a report for dismissal.

"I don't even have the moral right to ask Ukrainians for forgiveness"

After the mobilization announced by Putin, Yefremov said, he realized that he, as an officer who had already been in Ukraine, would not be left alone.

Konstantin contacted the human rights group Gulagu.net, which helped him leave Russia.

"I apologize to the entire Ukrainian people that I came to their house as an uninvited guest with a weapon in my hands.

And I thank God that no one was hurt by my hands, that I did not deprive anyone of life on that land.

And I thank God that I myself was not hurt.

I don't even have the moral right to apologize to Ukrainians.

I can't even apologize for myself, and I don't expect them to forgive me.

I never want and will not participate in such madness," the BBC quoted Konstantin Yefremov as saying.

The Russian Defense Ministry did not respond to a request for comment regarding Yefremov's allegations.

• The UN Human Rights Office documented cases of ill-treatment of prisoners during the war in Ukraine.

  It was noted that representatives of the organization interviewed more than 400 prisoners of war, both Ukrainian and Russian.

  International experts said they found cases of torture and ill-treatment of prisoners of war on both sides.