The World Health Organization said Wednesday its inspectors identified some issues at a Russian COVID-19 vaccine production site, while Moscow insisted the problems had been resolved.
WHO approval has been sought for the Sputnik V jab created by Russia's Gamaleya research institute, which is already being used in 40 countries.
The U.N. health agency inspected four Sputnik V manufacturing sites.
On Wednesday, it released a summary report of its preliminary findings, detailing six issues found during its May 31 to June 4 visit to the Pharmstandard Ufa Vitamin Plant in Ufa, southern Russia.
The inspectors had concerns with the data integrity and testing results from monitoring during manufacturing and quality control, and with the monitoring and control of aseptic operation and filling.
The inspection identified issues with the traceability and identification of vaccine batches.
There were also concerns over the filling lines, sterility assurance, sterile filtration validation and the risks of cross-contamination.
Kremlin spokesperson Dmitry Peskov said there were "some shortcomings identified by the inspection group, and from what we know, they were taken into account and all that needed to be changed was changed.
"Of course the necessary controls by the control bodies are in place. It is obvious that this is the strictest control possible", he added.
The WHO said the plant had been informed of its findings.
"Communications have been initiated with the relevant manufacturer, the applicant and the respective national regulatory authority with the view that the preliminary findings outlined in this report are investigated and addressed as quickly as possible," the organization told Agence France-Presse (AFP).
The WHO's emergency use listing is the green light that gives countries, funders, procuring agencies and communities assurance that a vaccine has met international standards.
EUL paves the way for countries to approve and import a vaccine for distribution quickly, especially those states without an international-class regulator of their own.
It also opens the door for the jabs to enter the COVAX global vaccine distribution facility, which aims to provide equitable access to doses in poorer countries.
The Sputnik V vaccine is already being used in 40 countries, according to an AFP count.
Besides Russia, those nations include Argentina, India, Iran, Kenya, Mexico, Pakistan, the Philippines and the United Arab Emirates.