Hoax bomb threats, many of which appeared to originate from Russian email domains, were directed at polling locations in four battleground states — Georgia, Michigan, Arizona and Wisconsin — as Election Day voting was under way, the FBI said on Tuesday.

"None of the threats have been determined to be credible thus far," the FBI said in a statement, adding that election integrity was among the bureau's highest priorities.

At least two polling sites targeted by the hoax bomb threats in Georgia were briefly evacuated on Tuesday.