A top aide to Nigeria's President Muhammadu Buhari has warned Nigerians living in London to be careful and to show restraint, following killings in the city.

The killing of black people, especially those of Nigerian origin in London, was "worrisome and disturbing”, said Abike Dabiri-Erewa, the senior special assistant to Mr Buhari on foreign affairs and the diaspora.

A total of 50 black people, mainly young, are reported to have been stabbed or gunned down in London since January, her office said in a statement.

This included nine Nigerian youth killed in London and other parts of the UK, the statement added.

Ms Dabiri-Erewa had written a protest letter to the UK High Commissioner in Nigeria, demanding an investigation and justice, the statement said.