By Subir Bhaumik BBC correspondent in Calcutta

Five supporters of two leftist parties have died in clashes in the Indian state of West Bengal since fighting between the two erupted on Wednesday.

The clashes began in the Kultoli region of the Sundarban mangrove delta south of Calcutta.

Two supporters of the ruling Communist Party of India (Marxist) or CPI(M) party were killed in clashes on Thursday.

This followed the deaths of three supporters of the Socialist Unity Centre of India (Suci), another leftwing organisation, on Wednesday.

Suci members say their colleagues were killed in attacks by alleged CPI(M) supporters.

Counter claims

The CPI(M), leads the communist coalition state government in Calcutta.

The ruling party and the Suci have been fighting to dominate the delta region for many years.

West Bengal police say the clashes may intensify before the state's village council or "panchayat" elections are held early next year.

The Suci dominates the Kultoli region and their leaders allege the Marxists are trying to oust them from the area by using professional gangsters.

The Marxists say the Suci are harbouring criminals to expand their political base.