The schoolgirls are believed to be held in a remote part of Borno state
Nigerian police say peaceful rallies to demand the release of more than 200 schoolgirls seized by Islamist militants will be allowed, after earlier banning them.
But campaigners were warned to exercise caution during protests.
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.
The government earlier banned public protests across Nigeria after scuffles broke out last week between demonstrators organised under the #BringBackOurGirls and a new government-sponsored group called #ReleaseOurGirls.
Mr Mbu said that public protests had “degenerated” and were now a security threat.
“Protests on the Chibok Girls is hereby banned with immediate effect,” he said in a statement on Monday.
But a day later, another police statement denied issuing any protest banning order, insisting that they had only released an “advisory notice”.
It said that there was a risk of the protest rallies being attacked by “criminal elements having links with insurgents”.
Those wanting to attend such gatherings should “seek proper advice and guidance from the police” in order to “avoid any unpleasant circumstances”, the statement said.
The about-turn came as the #BringBackOurGirls groups sought a court order against the ban.
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.
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.