Tanzania's current natural gas reserves have risen to more than 10 trillion cubic feet (tcf) from a previous estimate of 7.5 tcf following major gas discoveries in the country's deep-water offshore region.

Energy and Minerals Minister William Ngeleja said in a newspaper advertisement on Thursday the east African country has earmarked some of its growing gas deposits for export.

"Three offshore gas fields have been discovered in the deep waters and plans are underway to appraise the gas fields for possible development," Ngeleja said.

This brings the total number of gas fields found in the country's offshore area to seven, Reuters reports.

Tanzania had previously discovered gas deposits in four areas -- Songo Songo island off the eastern coast, in nearby West Songo Songo, Mnazi Bay in southeastern Tanzania and Mkuranga near Dar es Salaam.

"Preliminary indications show that Tanzania may have sizable gas reserves of more than 10 trillion cubic feet which can beneficially be developed to meet our local demand and for export," he said.

Two of the natural gas discoveries are already supplying gas to the country's commercial capital, Dar es Salaam, to produce electricity and power industries.

Ngeleja said there were 15 exploration companies searching for oil and gas in the country.

Interest in east Africa as a new hydrocarbon region has been heating up in recent years after major discoveries of oil in Uganda and natural gas in Tanzania and Mozambique.

NEW PIPELINE

"Exploration for petroleum started way back in the 1950s, and although we have not discovered liquid hydrocarbons, natural gas has been discovered in a number of places in our sedimentary basins in the country," he said.

Tanzania is seeking a $1.06 billion loan from China to build a natural gas pipeline from Mtwara region in the southern part of the country to Dar es Salaam, following a sharp rise in energy demand for power generation.

"The new pipeline is deemed to be a priority and strategic project for the government in pursuit of securing sufficient natural gas," the minister said in the statement.

He said implementation of the pipeline project, which would enable thermal power plants to switch from expensive oil imports to natural gas, was expected to start in December.

A study by the East African Community shows a separate pipeline to move natural gas from Dar es Salaam to the Kenyan port city of Mombasa would cost up to $630 million.

The state-run Tanzania Petroleum Development Corporation (TPDC) said on its website more than 50 hydrocarbon wells were at various stages of exploration and development in the country.

Brazilian petroleum company Petrobras was expected to start exploration this month for oil and gas off the coast of Tanzania, which is known to have significant gas deposits.

Tanzania has postponed its fourth deep offshore bidding round to next year to allow it to offer new blocks discovered by its latest seismic survey.

Initially scheduled for April, it was expected to invite bids for 13 deep offshore blocks located around 1,200 and 3,000 metres below sea.