The deal, valued at an estimated 400 billion rupees (8.5 billion dollars), includes a mega chemical industrial estate, expressways, townships, bridges and small and medium scale industries, said Sarit Banerjee, an official from the West Bengal chief minister's office.

It was signed between representatives of the West Bengal Industrial Development Corporation and New Kolkata International Development Pvt Ltd Monday and will be implemented in stages over the next 15 years, he said.

New Kolkata International Development is a company floated by Indonesia's 30 billion dollar Salim Group and two collaborators.

These include the Jakarta-based Universal Success headed by non-resident Indian Prasoon Mukherjee and the New Delhi-based construction major Unitech.

The project is expected to start soon with an initial investment of 34 billion rupees (723 million dollars), Banerjee said.

Talking to reporters after clinching the deal, West Bengal's reformist chief minister Buddhadeb Bhattacharjee said private investment was crucial for development.

"The people of Bengal are waiting for us to perform. Our government is trying to strike a balance between industry and agriculture to take the state forward."

Bhattacharjee said he was "aware of what the (state) opposition (parties) are saying about the project".

West Bengal's main opposition Trinamool Congress party has been opposed to the entry of private players into infrastructure development as have some members of Bhattacharjee's own Communist Party of India-Marxist (CPI-M) and other Left parties.