For the last three weeks, Buddhist-majority Myanmar has systematically slaughtered civilians belonging to the Rohingya Muslim minority, forcing 270,000 to flee to neighboring Bangladesh — with Myanmar soldiers shooting at them even as they cross the border.

“The Buddhists are killing us with bullets,” Noor Symon, a woman carrying her son, told a Times reporter. “They burned houses and tried to shoot us. They killed my husband by bullet.”

Daw Aung San Suu Kyi, the widow who defied Myanmar’s dictators, endured a total of 15 years of house arrest and led a campaign for democracy, was a hero of modern times. Yet today Daw Suu, as the effective leader of Myanmar, is chief apologist for this ethnic cleansing, as the country oppresses the darker-skinned Rohingya and denounces them as terrorists and illegal immigrants.

And “ethnic cleansing” may be an understatement. Even before the latest wave of terror, a Yale study had suggested that the brutality toward the Rohingya might qualify as genocide. The U.S. Holocaust Museum has also warned that a genocide against the Rohingya may be looming.

Burmese soldiers round up Rohingya in Rakhine State. Footage acquired by The New York Times

For shame, Daw Suu. We honored you and fought for your freedom — and now you use that freedom to condone the butchery of your own people?

“They’re killing children,” Matthew Smith, the chief executive of a human rights group called Fortify Rights, told me after interviewing refugees on the Bangladesh border. “In the least, we’re talking about crimes against humanity.”

“My two nephews, their heads were cut off,” one Rohingya survivor told Smith. “One was 6 years old and the other was 9.”

Other accounts describe soldiers throwing infants into a river to drown, and decapitating a grandmother. Hannah Beech, my Times colleague who has provided outstanding coverage from the border, put it this way: “I’ve covered refugee crises before, and this was by far the worst thing that I’ve ever seen.”

Rohingya refugees walk through rice fields after crossing over to the Bangladesh side of the Myanmar border on Friday. Bernat Armangue/Associated Press

It’s not that Daw Suu is organizing the killings (she does not control the military), or that they are entirely one-sided. The latest slaughter began after Rohingya militants attacked police stations and a military base on Aug. 25; the Myanmar security forces responded with scorched-earth fury against Rohingya civilians.

Footage acquired by The New York Times.

Hundreds are believed to have been killed, but Daw Suu has not criticized the slaughter. Rather, she blamed international aid groups and complained about “a huge iceberg of misinformation” aiming to help “the terrorists” — presumably meaning the Rohingya.

When a Rohingya woman bravely recounted how her husband had been shot dead and how she and three teenage girls had been gang-raped by soldiers, Daw Suu’s Facebook page mocked the claims as “fake rape.”

Based on a conversation with Daw Suu once about the Rohingya, I think she genuinely believes that they are outsiders and troublemakers. But in addition, the moral giant has become a pragmatic politician — and she knows that any sympathy for the Rohingya would be disastrous politically for her party in a country deeply hostile to its Muslim minority.

“We applauded Aung San Suu Kyi when she received her Nobel Prize because she symbolized courage in the face of tyranny,” noted Ken Roth, executive director of Human Rights Watch. “Now that she’s in power, she symbolizes cowardly complicity in the deadly tyranny being visited on the Rohingya.”

Another Nobel Peace Prize winner, Archbishop Desmond Tutu, wrote a pained letter to his friend: “My dear sister: If the political price of your ascension to the highest office in Myanmar is your silence, the price is surely too steep.”

A Rohingya child is carried in a sling after his family entered Bangladesh. Bernat Armangue/Associated Press

Myanmar tries to keep foreigners out of the Rohingya areas, but I’ve managed to get there twice in the last few years, and even then Rohingya were confined to concentration camps or to remote villages. Many were systematically denied medical care, and children were barred from public schools. It’s a 21st-century apartheid.

I saw a 23-year-old woman, Minura Begum, lose her baby because she needed a doctor; I met a brilliant 15-year-old girl whose dream of becoming a doctor is collapsing because she is confined to a concentration camp; I met a 2-year-old boy, Hirol, who was starving after his mother died for lack of medical care.

Daw Suu and other Myanmar officials refuse to use the word “Rohingya,” seeing them as just illegal immigrants from Bangladesh, but that’s absurd. A document from 1799 shows that even then, the Rohingya population was well established.

In Washington, Senators John McCain and Dick Durbin have introduced a bipartisan resolution condemning the violence and calling on Daw Suu to work to halt it. I hope President Trump speaks up as well.

We know that the Myanmar government responds to pressure, because that’s what won Daw Suu her freedom. Yet there has been far too little outcry for the Rohingya; bravo to Pope Francis for being an exception among world leaders and speaking up for them. A basic lesson of history: Ignoring a possible genocide only encourages the persecutors.

There are petitions online calling for Daw Suu to be stripped of her Nobel. In fact, there is no mechanism to take away the prize, but I do wish that the prize money could be recovered and go to feed the widows and orphans being created on her watch.