Indian Prime Minister Narendra Modi on Thursday condemned the alleged sexual assault of women in Manipur state as “shameful” and promised tough action, his first comments on ethnic clashes in the remote northeast which have killed at least 125 people.

The clashes began in early May and much of the violence was put down by the middle of that month.

However, sporadic violence and killings resumed soon afterwards and the state of 3.2 million people, which shares a border with Myanmar, has remained tense since. Hundreds have been injured and more than 40,000 have fled their homes.

The violence began on May 3 after a court ordered the state government to consider extending special economic benefits and quotas in government jobs and education enjoyed by the tribal Kuki people to the majority Meitei population as well.

Modi, who had not made any public remarks about the trouble in a state ruled by his Hindu nationalist Bharatiya Janata Party (BJP), spoke a day after videos showing women being molested in Manipur surfaced and sparked national outrage.

The videos on social media purport to show two women paraded naked and assaulted on a street before what townspeople on the videos say was a gang rape.

Reuters could not immediately verify the authenticity of the videos.

“My heart is filled with pain, it is filled with anger,” Modi said at the end of customary comments he makes before the start of each session of parliament. “The incident from Manipur that has come to the fore, it is shameful for any civil society.”

“The law will take its strongest steps, with all its might. What happened to the daughters of Manipur can never be forgiven,” he said and urged chief ministers of all states to strengthen law enforcement.

Just as Modi concluded his statement, Manipur Chief Minister Biren Singh tweeted that state police have made the first arrest in the case.

“A thorough investigation is currently underway and we will ensure strict action is taken against all the perpetrators, including considering the possibility of capital punishment,” said Singh, who has been accused by rights groups and some of his own BJP lawmakers of failing to tackle the violence.

Manipur police said they have opened a case of gang rape and arrested a man, adding that others will be held soon.

A preliminary probe showed that the assault on the two women took place on May 4 but videos of them being dragged, groped and paraded naked by armed miscreants went viral on Wednesday, police said.

India’s highest court said it was deeply disturbed by the images and asked the government to inform the court of the steps taken to apprehend the perpetrators and ensure such incidents were not repeated.

“In a constitutional democracy it is unacceptable,” said Chief Justice of India D.Y. Chandrachud.