Mikhail Fedotov, the head of the Kremlin's human rights council, said at a press conference that he was waiting for permission from investigators to visit the suspect, former Chechen police officer Zaur Dadayev tomorrow.
Nemtsov, 55, an ex-deputy prime minister who became an outspoken critic of President Vladimir Putin, was shot four times in the back near the Kremlin on February 27 in the most shocking assassination of an opposition leader during Putin's 15 years in power.
But yesterday a member of the Kremlin's rights council, Andrei Babushkin, said after a jail visit to Dadayev that the suspect now insists he is innocent, and may have confessed under torture.
"We cannot confirm that he was tortured as we are not investigators, but we did find numerous wounds on his body," Babushkin told AFP.
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Those allegations sparked a fierce reaction from Russia's powerful Investigative Committee, which is probing the shooting. Both Babushkin and a journalist who spoke to Dadayev were questioned by investigators over possible interference in a criminal case.
Nemtsov's murder sent shock waves through the opposition, which accuses Putin of steadily suppressing dissent. Regime opponents also allege the Kremlin was behind the murder of one of its last outspoken critics.
Investigators have said they were looking into the possibility that the former deputy prime minister was killed over his support of French satirical magazine Charlie Hebdo, which published images of the Prophet Mohammed and was attacked in January.
But close Nemtsov allies in Russia's marginalised opposition dismissed that claim as "absurd."