NAIROBI, September 9, 2008 (AFP) - London Stock Exchange-listed Petra Diamonds has bought a 75-percent stake in Tanzania's Williamson diamond mine for 10 million dollars (seven million euros) from De Beers Group, it said Tuesday.

'The acquisition is in line with the (Petra Diamonds') aim of creating a diamond production portfolio of global significance, complemented by a substantial and valuable resource base,' it said in a statement.

'Williamson (north of Tanzania) will add a further major mine to our portfolio, with the potential to deliver considerable value to our shareholders,' said Petra chief Johan Dippenaar in the statement.

'This acquisition also marks Petra's entry into Tanzania, further diversifying the group's geographical spread across Africa,' he added.

The Tanzanian government owns the remaining 25 percent of the diamond mine measuring 146 hectares.

Tanzania's mining sector has expanded rapidly over the past decade after it adopted liberal economic policies in the mid-1980s.