Nigerian police have banned public protests in the capital Abuja for the release of more than 200 schoolgirls seized by Islamist militants in April.
Abuja police commissioner Joseph Mbu said the rallies were "now posing a serious security threat".
Nigeria has seen almost daily rallies calling for the government to take firmer action to rescue the girls.
Boko Haram militants snatched the girls from the remote Chibok village near the Cameroon border on 14 April.
In a statement, Mr Mbu said that public protests had "degenerated" and were now a security threat.
He was also quoted by the state-run Agency of Nigeria as saying that "dangerous elements" could join the demonstrations.
Nigeria's government has been facing growing pressure both at home and abroad to do more to tackle the group and bring about the girls' release.
A deal for the release of some of the abducted schoolgirls in Nigeria was close to being secured when the Nigerian government called it off late last month, the BBC has learned.
Some of the girls were set to be freed in exchange for imprisoned Islamist militants, reports the BBC's Will Ross.
Thousands of people have died since Boko Haram began a violent campaign against the Nigerian government in 2009 and in the subsequent security crackdown.
The girls, who were mainly Christian, were taken from their school in Chibok, in north-eastern Borno state and are thought to be held in a remote forested area of the state, close to the border with Chad and Cameroon.
Last month, Boko Haram released a video of some of the girls. The footage was interspersed with militants explaining that the girls had "converted" to Islam.
The UK, the US, China and France are among the countries to have sent teams of experts and equipment to help to locate them.
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Video - The state of Nigerian governance and Boko Haram