In its first report, FIFA's newly-branded Human Rights Advisory Board issued a warning over "significant risks to workers' rights in the final phases of the construction in Russia".
FIFA admitted in May that it had evidence that North Koreans were working on venue construction in St. Petersburg.
The revelations raised alarm as Stalinist North Korea is known to export workers to projects where slave-like conditions are enforced.
However, the extent of the problem in Russia remains difficult to assess, the rights panel said, noting that the "monitoring systems" set up by FIFA and the organising committee had been undermined by weak transparency.
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The eight-member board underscored that it wanted more information concerning "North Korean workers that could be connected to 2018 FIFA World Cup construction sites."
Allegedly abusive conditions facing migrant workers in World Cup 2022 host Qatar have also triggered criticism of FIFA.
The UN's International Labour Organisation (ILO) on Wednesday closed its investigation of the gas-rich emirate over possible worker abuses, saying Qatar's labour reform plan had addressed the problem.
"Irrespective of any decision taken by the ILO, the (rights panel) noted that it is incumbent on FIFA - with its direct connection to the 2022 FIFA World Cup construction underway in the country - to have a clear position on the rights of migrant workers in Qatar", the report said.
FIFA needed "to ensure that the legal protections they are afforded are in line with international labour rights standards."
The eight-member group includes leaders from labour unions, international NGOs, human rights experts and officials from FIFA commercial partners.