Bangladeshi police said on Tuesday that 450 people had been arrested in the Muslim-majority nation after attacks against Hindus in some of the worst such unrest for over a decade.

At least six people have died, local media reported, as police have fought to restrain angry mobs.

The violence began on Friday when hundreds of Muslims protested in the southeastern Noakhali district accusing Hindus of a blasphemous incident involving the Koran.

Several Hindu religious sites have been vandalised, and homes attacked.

Authorities have filed 71 cases in connection with the violence during the Hindu festival of Durga Puja, a Bangladesh police spokesman said. Investigations were ongoing after the arrest of 450 suspected culprits, he added.

Communal tensions have long simmered in Bangladesh, whose constitution designates Islam as the state religion but also upholds the principle of secularism.

Hindus make up around 10% of the population.

The unrest is among the worst in Bangladesh since Prime Minister Sheikh Hasina’s Awami League party came to power in 2009.

“Recent attacks on Hindus of Bangladesh, fuelled by hate speech on social media, are against the values of the Constitution and need to stop,” tweeted Mia Seppo, the United Nations’ resident coordinator in Bangladesh.

Rights group Amnesty International called for an investigation and punishment for perpetrators.