Militants in the oil rich Niger Delta have demanded the government prove one of their leaders is alive.
Nigerian President Umaru Yar'Adua denied claims Henry Okah died in police custody on Tuesday.
Lawyers, family members and doctors should be allowed to see him, the Movement for the Emancipation of the Niger Delta (Mend) said.
Mr Okah was extradited from Angola last week on gun-running charges, but he has not appeared in court yet.
Mend had sent an e-mail to reporters saying he was shot "accidentally" during interrogation.
But the president's spokesman said Mr Okah was "in safe custody"
After the government denied the report, Mend sent a follow up email to journalists.
"The government must go a step further, (give) access to his legal representatives, family, pastor and the International Red Cross or similar body for an independent verification that he is alive and has never been tortured," the email said.
Presidential spokesman Segun Adeniyi refused to comment on the new demand.
Mr Okah is a founder member of Mend, which carried out attacks in the Delta two years ago that cut Nigerian oil production by a quarter.
Since then the group has factionalised and some leaders have halted attacks after striking deals with the government, although Mr Okah's faction has remained active.
(BBC)
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