Nigerian President Muhammadu Buhari says he is not demanding "any apology from anybody" after UK Prime Minister David Cameron labelled his country "fantastically corrupt".

Speaking at an anti-corruption event in London, Buhari said he was more interested in the return of stolen assets held in British banks.

Prime Minister Cameron made the unguarded comments in a conversation with the Queen.

He is hosting an international anti-corruption summit on Thursday.

Nigeria was ranked 136th in Transparency International's 2015 Corruption Perceptions Index.

Asked at the event if Nigeria was "fantastically corrupt", Buhari replied: "Yes".

In his speech, the Nigerian leader described corruption as a "hydra-headed monster" which threatened the security of countries and "does not differentiate between developed and developing countries".

He said corruption in Nigeria was endemic and his government was committed to fighting it.

The UK government will host world and business leaders at the summit on Thursday in London, aiming to "galvanise a global response to tackle corruption".

Speaking ahead of the summit, Cameron said: "For too long there has been a taboo about tackling this issue head-on.

"The summit will change that. Together we will push the fight against corruption to the top of the international agenda where it belongs."