There are tensions between the ICC and the AU, with some on the continent accusing the court of unfairly targeting Africans. The AU has previously urged the ICC to stop proceedings against sitting leaders.

The warrants against Mr Bashir, who denies the allegations, have restricted his overseas travel.

He has, however, visited friendly states in Africa and the Middle East.

South Africa has often shied away from this sort of diplomatic headache, but this time the government has stepped straight, and deliberately, into controversy, courting Western fury by rolling out the welcome carpet for President Bashir.

The South African government must, surely, have foreseen the possibility of a legal challenge. If President Bashir is allowed to return home unimpeded, South Africa’s actions will be bitterly condemned internationally – if less loudly within the continent – as a blow against the credibility of the ICC.

And if Sudan’s president is detained, or perhaps even arrested, then Pretoria will be accused of luring a fellow African leader into a trap. Some would call that a no-win situation.

But it’s clear that South Africa’s government has chosen to flaunt its growing antipathy towards “Western” rules, and towards a court in which so many African leaders now appear to have lost faith.

The ICC has issued two arrest warrants against Mr Bashir. The court relies on member states to carry out arrests.

However correspondents have said the South African government – a signatory to the treaty establishing the ICC – is unlikely to move against the Sudanese leader.

South Africa’s governing African National Congress said immunity had been granted to “all (summit) participants as part of the international norms for countries hosting such gathering of the AU or even the United Nations”.

The ANC also said the ICC was “no longer useful for the purposes for which it was intended”.

The court, which sits in The Hague in the Netherlands, was set up in 2002 to try cases of genocide, crimes against humanity and war crimes, when national courts cannot handle them.

Human rights organisations and South Africa’s main opposition party have also called for Mr Bashir’s arrest.

Darfur has been in conflict since 2003, when rebels took up arms against the government. The UN says more than 300,000 people have died, mostly from disease. Hundreds of villages have been attacked.

More than two million people – about a third of the population – have fled their homes. Sudanese forces and allied militias are accused of oppressing black Africans in favour of Arabs.

The Johannesburg summit is chaired by Zimbabwean President Robert Mugabe, who holds the rotating presidency of the AU. The official theme is Year of Women’s Empowerment and Development.

But the political turmoil in Burundi, crisis in South Sudan and the recent spate of xenophobic attacks in South Africa are also likely to feature heavily.