Malala has condemned a “horrifying” ban on female students wearing the hijab to school in the southern Indian state of Karnataka, as schools there shut for three days following violent clashes between protesting Muslims and Hindu mobs.

Groups of Hindus were filmed storming school campuses around the state and raising saffron flags, a colour considered holy in Hinduism, while Muslim students fled, causing condemnation from neighbouring Pakistan.

At least 18 people were arrested Tuesday in the town of Banahatti after groups of Muslims and Hindus clashed and threw stones, according to the Indian media. Tear gas and baton charges were also deployed to break up demonstrations in several towns and cities.

“Refusing to let girls go to school in their hijabs is horrifying,” wrote Malala Yousafzai, Nobel laureate and women’s education activist on Tuesday evening. “Objectification of women persists – for wearing less or more.”

Ms Yousafzai added India’s Hindu nationalist ruling Bharatiya Janata Party (BJP) must stop the “marginalisation of Muslim women” to avoid further intercommunal conflict.

A group of Muslim girls began a sit-in protest at their college in the city of Udupi in January after their principal refused to let them attend lessons while wearing the hijab.