Protests over a now-disbanded police unit, the Special Anti-Robbery Squad (Sars), have been taking place in Nigeria for two weeks.
They began with calls for the unit, which had been accused of illegal detentions, assaults and shootings, to be disbanded.
President Buhari dissolved it on 11 October.
Since then, the demonstrators have called for more changes in the security forces as well as reforms to the way the country is run.
A number of people taking part in a protest against police brutality were reportedly shot dead or wounded on 21 October in Nigeria's biggest city, Lagos.
Witnesses said up to 12 people were killed and others wounded when soldiers opened fire. Amnesty International said it had "credible reports" of deaths.
The state governor, however, said there had been no fatalities, although about 25 people had been wounded.
In London too, protesters have been out on the streets in recent days.
Protests have also been been taking place outside various embassies, including in Nairobi, Kenya (below)...
...and at the Nigerian embassy in Pretoria, South Africa (below).