British security firm G4S has confirmed that it is to end all of its Israeli prison contracts within the next three years.

"We expect them to expire and we don't expect to renew them," said G4S chief executive Ashley Almanza.

The contracts held by G4S in Israel include the provision of security at military checkpoints, prisons - such as the controversial Ofer prison where two teenagers were killed on Nakba Day last month - and a West Bank police station, all of which expire in 2015.

The company provides security services and equipment at Israeli prisons where allegations of child torture, forced confessions, overcrowding and medical neglect have been raised.

The company employs 8,000 people in Israel but claims to have no workers based at prison sites or in control of prisons in the occupied West Bank.

"We do not operate prisons, we supply prisons with security equipment," said Almanza, adding that G4S equipment made prisons safer and did not increase the risk of alleged human rights abuse.

The reasons for G4S not renewing the controversial contracts remain unknown, but an annual general meeting held by the company was this week disrupted by 25 protesters who had bought shares in the company in order to attend.

The decision comes after an independent report, published this week, asserted that the company "had no causal or contributory role in human rights violations."

"There are clearly human rights failings in some parts of Israel's security system, but G4S's role is far removed from their immediate causes and impact," said the report by Hugo Slim, a research fellow at Oxford University's Institute of Ethics, Law and Armed Conflict.

Bill Gates has sold off a portion of his shares in G4S after his philanthropic body, the Bill and Melinda Gates Foundation, was accused of complicity in the torture of Palestinian prisoners through its investment in the company.

The foundation, the largest in the world, last year purchased £110m ($172m) worth of shares in G4S, something that human rights charities, such as Addameer Prisoner Support, claim contradicted the foundation's belief that "every life has equal value".

More than 5,000 Palestinians, including 183 children, are currently held in detention in Israeli prisons.

No one at G4S was immediately available to comment on the decision.