Archbishop Emeritus Desmond Tutu, the South African activist who fought to end apartheid, has joined a worldwide campaign calling on corporations profiting from Israel's occupation of Palestinian Territories to pull out their funding.

Tutu is among 1.5 million people who have joined the initiative, launched by the global campaign organisation Avaaz, as Israel continues its offensive against the Gaza Strip.

The campaign targets companies including Hewlett Packard, G4S, Caterpillar, ABP and Veolia, which are either directly or indirectly financing activities in the occupied territories that serve Israeli settlements which are illegal under international law.

Tutu said: "The withdrawal of trade with South Africa by multinational corporations with a conscience in the 1980s ultimately brought the apartheid state - bloodlessly - to its knees.

"Those corporations understood that by contributing to South Africa's economy, they were contributing to the repression of black South Africans.

"So they cut off apartheid's oxygen supply. Where the world's political and diplomatic leaders had failed, civil society succeeded.

"The crisis we are witnessing in Gaza today is not a Jewish or a Muslim crisis. It is a human crisis.

"Those who continue to do business with Israel fund the perpetuation of a profoundly unjust status quo.

"Those who withdraw their business are saying Israelis and Palestinians are equally entitled to dignity and peace. Gaza is going to test who believes in the worth of human beings."

The call for divestment comes after several public pull-outs in recent months.

Dutch pension fund PGGM withdrew tens of millions of euros from Israeli banks, the Bill and Melinda Gates Foundation divested from security firm G4S, and the US Presbyterian Church divested an estimated $21m from HP, Motorola Solutions, and Caterpillar.

It also follows warnings issued earlier in July by 17 EU governments urging their citizens to avoid doing business in or investing in illegal Israeli settlements.