Niger opposition activist Marou Amadou has been mistreated in custody by security forces, members of his association say.
Mr Amadou's associates said he had to be treated at a prison clinic on Wednesday before being questioned.
He was taken into custody on Tuesday hours after he was freed by a court on charges of breaching state security.
There was no immediate comment on the claims from authorities, and calls to the justice ministry were unanswered.
Fellow activists say they saw Mr Amadou - a critic of the president's plan to extend his rule - through the prison gates and that he appeared to have sustained injuries.
Officials at the police station where Mr Amadou was thought to have been taken told the BBC's Idy Baraou that the activist was not present and did not comment on the allegations.
Mr Amadou was abducted on Tuesday, hours after he was freed by a court after calling for protests against a new constitution extending the president's term.
Members of his association - the United Front for the Protection of Democracy (Fusad) - said he had been taken to an unknown location by members of the Republican Guard.
Fusad is allied to opposition parties that have been campaigning against a new constitution that extends President Mamadou Tandja's term by three years.
Members of Fusad including its secretary-general, Maman Wada, said Mr Amadou had been beaten up after being abducted.
But they said they had not been able to visit Mr Amadou and did not give details about the nature of the mistreatment.
They said Mr Amadou had been taken from prison to the police station on Wednesday morning, but police had sent him back to the prison clinic when they saw he was not in a fit state to be questioned.
Local human rights campaigners said he had then been taken once more to the police station, where there was a heavy security presence.
Earlier, a government spokesman was quoted by French radio network RFI as saying that Mr Amadou was safe, and that he would be kept in prison because the public prosecutor had lodged an appeal.
Niger's new constitution, which was approved in a referendum on 4 August, allows Mr Tandja to run in subsequent elections, potentially giving him the opportunity to stay in power for life.
The EU and France have criticised the referendum and called on Niger to restore a democratic framework.
Thursday, August 13, 2009
Niger opposition figure 'beaten'
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