(IDEX Online) - Petra Diamonds says illegal incursions at its Williamson mine, in Tanzania, are averaging more than one a day.The UK-listed miner announced in May that it had agreed a $6m settlement over alleged human rights breaches at the deposit, which is currently mothballed and classified as "an asset held for sale for financial reporting purposes".In a quarterly update to alleged human rights abuses at the mine, Petra said: "There were a total of 143 reported incidents of illegal incursions onto the Williamson mine lease area, resulting in six security officials and two police officials suffering minor injuries and 15 arrests being made."It said was continuing its extensive engagement with local communities to highlight the dangers of illegal mining, and to reduce illegal incursions, especially by under-age miners.Petra's own investigation concluded that the security teams it formerly employed to protect the sprawling of 30km2 kimberlite resource from illegal miners had been responsible for some deaths and many injuries.Pic shows Williamson mine.