In a striking addition to his recent appeals for justice and compassion for Africa, Pope Benedict XVI has urged the world's richest nations to cancel the foreign debt of developing countries, specifically those on the African continent. He says helping the poorest countries to overcome poverty and wipe out Aids is the "grave and unconditional responsibility" of the wealthiest nations.

In a just-published letter that was sent last December to the German Chancellor, Angela Merkel, the Pope says that Europe and the countries belonging to the G8 should take the lead and give "the highest attention and priority" to assisting the developing world.

The papal letter was sent as Germany took over the presidency of both the European Union and the G8 - the group of seven leading economic powers plus Russia - but was not made public by the Vatican until this week. Both the Pope's Urbi et Orbi message and a subsequent address to a UN population and development conference by the Vatican's UN observer Archbishop Celestino Migliore focused particularly on the needs of Africa, while the Pope's latest book, Jesus of Nazareth, draws attention to global economic inequalities that blight Africa in particular. "I welcome the fact that the question of poverty, with specific reference to Africa, now appears on the agenda of the G8," the letter says. The G8 holds its next meeting in the Baltic Sea resort of Heiligendamm, near Rostock, on 6-8 June.

According to a report in The Guardian this week, the Africa Progress Panel, set up by Tony Blair to monitor the results of the 2005 G8 summit at Gleneagles, has found that the rich nations, who promised $US50 billion of development assistance by 2010, currently had met only 10 per cent of that target total.

The Pope calls for a "substantial investment of resources" for medicines to treat Aids and other diseases, saying that the "first and foremost" concern should be the development of a vaccine against malaria. He also urges the international community to "continue to work for the substantial reduction of both the legal and illegal arms trade", as well as an end to money laundering, the pillaging of precious raw materials and the flight of capital from poor countries.

Chancellor Merkel's response to the Pope, dated 2 February, was also made public by the Vatican. "For me it is crucial that G8 relations with Africa move towards a reform partnership," Mrs Merkel wrote. "Alongside increased efforts on the part of African countries, we attach importance to greater commitment of the international communities ... Our aim is to change the strategies for combating HIV/Aids so that they take special account of the situation of women and girls."

The Pope's letter highlights concerns of many Catholic groups, including "Religious Debt Coalition", a Rome-based coalition of more than 80 religious orders and 162 member organisations of Caritas Internationalis that has been pressing the G8 for six years to cancel debts of poor nations, arguing that debt cancellation has worked where it has been tried.