Amnesty International on Friday called on the Nigerian authorities to launch immediate investigations into the assault and detention of three human rights activists by police in the city of Port Harcourt.
Isaac Asume Osuoka, AkpoBari Celestine and Ken Henshaw from non-governmental organization Social Action, which campaigns for environmental justice and human rights in Nigeria, were stopped and detained by police on 5 April after leaving their office.
AkpoBari Celestine said he was repeatedly hit with the butt of a gun, poked with a barrel in his arms and legs and slapped in the face, as at least six armed men, including at least three uniformed police officers, forced the activists out of their car and into a white van without asking the victims for any form of identification.
The three men were not told why they were stopped and detained but were taken to Olu Obasanjo police station in Port Harcourt.
"They knew who we were," said Isaac Asume Osuoka.
"When we were stopped they didn't ask for our names, they didn’t ask to see a driver's licence, they didn't ask for any car documents."
At the police station, the activists were refused access to legal counsel.
AkpoBari Celestine said he was denied medical treatment for the injuries sustained while being detained.
The activists were released without charge around midnight, after alerting friends and colleagues in the city who intervened on their behalf.
"The excessive use of force and arbitrary detention suffered by these men must be fully investigated and the perpetrators brought to justice," said Erwin van der Borght, director of Amnesty International's Africa programme.
The clinic where AkboBari Celestine sought treatment following his release later refused to give him the medical report that detailed his injuries, the activists believe staff at the clinic may have been intimidated by the police.
A Medical report carried out in Austria, where the activist is holding talks about human rights in the Niger Delta, found that he sustained several bruises on his arms and legs from the beating he received from the police.
"The government must ensure that human rights defenders can carry out their work without interference, obstacles, discrimination or fear of retaliation," said Erwin van der Borght.
"These activists have a right to an independent, impartial and competent review of complaints and, where violations are found to have taken place, to obtain redress."
The Nigeria Police Force (NPF) continues to commit a wide range of human rights violations with impunity, including unlawful killings, torture, other ill-treatment and enforced disappearances.
Some people are targeted for failing to pay bribes and several have been tortured to death in police detention.