Indian Prime Minister Narendra Modi says India's is the fastest growing economy, but Africa is also developing rapidly.

Although India's headline economic growth has overtaken China's, its economy is one-fifth the size and it lacks the financial heft to challenge Beijing in a head-to-head contest for the African market.

"We can't match the Chinese in terms of resources - but any engagement we do with the Africans at least gives them a choice," said C Raja Mohan, a foreign policy commentator at the Observer Research Foundation in New Delhi.

The India-Africa Forum Summit is the third of its kind and, since the first was held in 2008; two-way annual trade has more than doubled to $72 billion.

That lags trade between China and Africa, which has exploded to $200 billion as the world's No.2 economy sucks in coal, oil and metals to feed their industrial machine.

The world's largest democracy has been criticised by human rights groups for inviting Omar al-Bashir, the president of oil-rich Sudan wanted by the International Criminal Court on charges of war and crimes against humanity and genocide in Darfur.

For India, business comes first. The State-run oil company ONGC, which has fields in Sudan and South Sudan, is on the hunt to buy $12 billion in foreign assets over the next three years and has identified Africa as an investment target.

India is also in talks with South Africa to buy coal mines producing up to 90 million tonnes of cooking coal each year. South Africa is already a major coal supplier to India.

India wants its involvement in Africa to be less transactional than China's, seeking a development partnership for two regions that account for a third of the world's people, but seven in 10 of those living in poverty.

"Our partnership is not focused on an exploitative or extraction point of view, but is one that focuses on Africa's needs and India's strengths," said Vikas Swarup, spokesman for the Indian Ministry of External Affairs.

Trade ministers from India and Africa are looking to make common cause at a World Trade Organisation ministerial meeting in Nairobi next month, Commerce Minister Nirmala Sitharaman said.

Although India dropped its veto against a WTO deal to streamline customs procedures a year ago, it remains uneasy over Western pressure on food stockpiling it says is vital to ensure its 1.25 billion people don't go hungry.