The United Nations says that two of its experts have been blocked from investigating torture in The Gambia.
The government had agreed to allow the UN to look into allegations of extrajudicial executions and abuse of government opponents, journalists and activists.
But during their visit the experts were denied full access to prisons, the UN said.
The Gambia has been widely criticised for its poor record on human rights.
The UN investigators were prevented from visiting the high security wing of the Banjul prison where inmates condemned to death are held.
Special investigator, Christof Heyns, said in a statement that "an inference must be drawn that there is something important to hide".
Both investigators said that, during their three day visit in November, they had "received many reports that there are paramilitary hit squads in the country".
They also heard allegations of the widespread use of torture by The Gambia's National Intelligence Agency.
The investigators' final reports on their visit will be presented to the UN Human Rights Council in early 2015.