Ukrainian military forces stopped and seized a vehicle carrying three armed men transporting guns, ammunition, and an estimated 100,000 ballots for a May 11 referendum already marked "yes" for the eastern city of Donetsk to break away and form an independent state, Kyiv Post reports.

The men — which Ukrainian media have described as "armed terrorists" — were found with ballots in the trunk of their car on the outskirts of the city, a police source told the Ukraine Observer.

Many cities in eastern Ukraine have been under siege for about a month, including Donetsk, where the city's main government building and a number of schools have been seized by pro-Russian separatists believed to be backed by Moscow.

The new reports of fraudulent ballots brings to mind a similar incident in Crimea, the region recently annexed to Russia following a March 16 vote. A senior White House official told Reuters there was "concrete evidence" some of those ballots arrived to Crimean cities pre-marked.

The Russian government claimed the Crimea referendum resulted in a 96.7% vote in favor of annexation, although a Russian government agency later wrote on its website that turnout was only 30%, with only half voting in favor of annexation.

While the May 11 referendum seems to be moving forward as planned, even Russian President Vladimir Putin issued a surprising call to postpone the vote "in order to create the necessary conditions" for a dialogue between local representatives and authorities in Kiev, The Daily Beast reported.

"We are also very concerned about the efforts of pro-Russian separatists in Donetsk and Luhansk to organize a frankly contrived and bogus independence referendum on May 11," U.S. Secretary of State John Kerry said recently. "We flatly reject this illegal effort to further divide Ukraine."

This video has appeared in numerous Ukrainian media reports: