Last year, the firm said it was investigating allegations that artisanal miners who trespassed on the firm's Williamson mine in Tanzania were detained, beaten and shot at, killing at least seven of them.
The abuses were allegedly committed by security contractors and security employees of Petra's subsidiary Williamson Diamonds Limited (WDL).
"Petra Diamonds Limited today confirms that a settlement has been reached, on a no admission of liability basis," Petra said in a statement.
A London-based law firm, Leigh Day, had sued Petra in a London court on behalf of 71 claimants who alleged the human rights abuses.
Petra owns 75% of the mine, while the Tanzania government owns the rest. The firm said it had agreed to a settlement worth 4.3 million pounds ($6.1 million) that will cover direct compensatory payments to victims, their legal expenses, investments in community projects and others items.
The firm said its investigations had confirmed incidents at the mine that "regrettably resulted in the loss of life, injury and the mistreatment of illegal diggers."
($1 = 0.7084 pounds)
(Reporting by Elias Biryabarema; editing by David Evans)