Tanzania has invited bids to build a 2 100 MW hydroelectric plant in a World Heritage site renowned for its animal populations, despite opposition from conservationists to the long-delayed project.

The East African nation considers the project at Stiegler’s Gorge in the Unesco-designated Selous Game Reserve as vital in its bid to diversify its energy mix and end chronic electricity shortages. The project would more than double the country's power generation capacity.

The Energy and Minerals Ministry said it expected construction of the power plant to be completed within three years, according to a document published on its website late on Wednesday.

The deadline for bids is Oct. 16, according to the document, which specifies that work must be completed within a period of 36 months, with a maximum mobilisation period of three months.

The government did not say how much the project would cost and how it would raise financing.

President John Magufuli's office said last month the long-delayed hydroelectric plant would be built "to speed up the development of the country".

Experts from Ethiopia, which is also building new hydro-electric dams, would advise the government, Magufuli's office said.

Critics say construction of a dam in a major river that runs through the Selous Game Reserve could affect wildlife and their habitats downstream.

Covering 50 000 km², the reserve is one of the largest protected areas in Africa, according to Unesco. It is known for its elephants, black rhinoceroses and giraffes, among many other species.

The WWF conservation group said in a report in July the proposed large-scale hydropower dam "puts protected areas of global importance, as well as the livelihoods of over 200 000 people who depend upon the environment, at risk."

"The impact on Tanzania’s largest river would affect many ecosystem services it provides. It would affect tourism in Selous downstream in some of the most abundant wildlife areas in the game reserve," it said.

The government has also been criticised by environmental groups for granting Australia-based miner Mantra Resources rights to build a $400-million uranium mine in the sanctuary.

Tanzania said in February it needed $46.2-billion in investment over the next 20 years to revamp ageing energy infrastructure and to meet soaring demand for electricity.

Investors have long complained that a lack of reliable power is an obstacle to doing business in East Africa’s second biggest economy.

Tanzania aims to boost power generation capacity to 10 000 MW on the next decade from about 1 500 MW now by using hydropower and some of its vast natural gas and coal reserves.