Expressing anguish over incidents targeting north Indians in Mumbai, Union Chemicals and Fertilisers Minister Ram Vilas Paswan on Wednesday said he had written a letter to Prime Minister Manmohan Singh [Images] on the issue.

"I have written a letter to Prime Minister Manmohan Singh on February 4 highlighting that the issue is dangerous for the unity and intergrity of the nation and urged him to take stern action against (Raj) Thackeray," he told reporters in Gwalior on Wednesday.

Paswan demanded that the state government arrest the Maharashtra Navnirman Sena chief.

Paswan, who arrived in Gwalior to address a Lok Janshakti Party's rally, in reply to a question on election pacts, said his party will contest the assembly polls in Madhya Pradesh on its own.

Earlier addressing the rally attended by a large number of people, he criticised Uttar Pradesh Chief Minister Mayawati for her "changed" stance towards Brahmins for gaining "political mileage".

He said that because of poverty, hunger and unemployment, Naxalism has taken its roots in the country and added his party will address these issues to solve the menace.