Amnesty International says Nigeria is trying to muzzle dissent by arresting and intimidating journalists and protesters.

The London-based rights group cites examples of police blocking peaceful protests. Those protests include activists demanding the government rescue more than 200 kidnapped Chibok schoolgirls, Shiite Muslims demanding the release of their long-detained leader and separatists calling for an independent Biafra in the southeast.

The statement Wednesday says Amnesty has documented cases of enforced disappearances and killings of pro-Biafra supporters by security forces.

It also cites the detention of several journalists critical of officials in the government of President Muhammadu Buhari.

Amnesty says the intimidation appears to be "a barefaced attempt by the Nigerian government to muzzle dissenting voices."

It urges the government to halt detentions without trial and the excessive use of force.