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

The clashes began in early May and much of the violence was put down within days.

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 of people have been injured and more than 40,000 have fled their homes.