The Oklahoma secretary of state's office says it received a letter in August from Russia's consulate general in Houston seeking to have one of its officers present at a voting precinct to study the "US experience in organization of voting process."
But the office denied the request, noting Oklahoma law prohibits anyone except election officials and voters from being present while voting is taking place.
The Tulsa World newspaper reported Louisiana and Texas denied similar requests from Russian officials.
Republican presidential nominee Donald Trump has faced criticism for suggesting the election might be "rigged" and for praising Russian President Vladimir Putin.
This story has been corrected to reflect that the letter was received in August, not last month.
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