In an unprecedented warning, the United States said on Monday that it could blacklist individuals who committed serious irregularities reported during Armenia’s recent constitutional referendum.

In a fresh statement on the December 6 vote, the U.S. Embassy in Yerevan also renewed its calls for the Armenian authorities to investigate in earnest “credible allegations” of fraud that have been voiced by opposition activists and non-partisan monitors.

“We reiterate that the results of the investigations and prosecutions of those responsible for any irregularities must be transparent and public in order for the Armenian people to have confidence in the integrity of the electoral process,” it said. “Full and transparent investigations, as well as the resulting public reports, even if they do not lead to criminal prosecutions, can help the Electoral Commission, the National Assembly, and civil society identify possible improvements to current electoral procedures.”

“In accordance with the U.S. commitment to fight corruption worldwide, the U.S. Embassy can also draw upon the information contained in such reports to help assess whether any individuals who directly interfered in the integrity of the December 6 electoral process can participate in Embassy programs or activities,” added the statement.

The embassy did not specify whether those individuals could be banned from entering U.S. or have their possible assets frozen.

The U.S. has repeatedly criticized disputed elections and referendums held in Armenia in the past. But it is the first time that Washington is openly threatening to shun or sanction local election officials accused of vote rigging.

Richard Giragosian, a U.S.-born analyst based in Yerevan, suggested that the embassy warning is “the first step towards sanctions” against Armenian officials. He compared it to U.S. visa bans and asset freezes imposed on Russian officials involved in the alleged cover-up of the death of Sergei Magnitsky, a lawyer who died in prison in 2009 after exposing large-scale corruption in Russia.

“This may be the opening round for such harsh but individual-targeted sanctions,” Giragosian told RFE/RL’s Armenian service (Azatutyun.am).

The U.S. mission issued the statement three days after Prosecutor-General Gevorg Kostanian briefed reporters on ongoing investigations into referendum-related fraud claims investigated by Armenian law-enforcement authorities. Kostanian said that while they have opened 14 criminal cases in connection with the allegations, nobody has been arrested or charged yet.

Kostanian said the Armenian police and other law-enforcement bodies received over 460 complaints relating to the conduct of the referendum. “A fraud report does not necessarily mean a fact of a crime,” he stressed.

The deputy head of Armenia’s Investigative Committee, Aram Tamazian, made a similar point at a news conference on Monday. “The number of [fraud] reports does not necessarily indicate as many violations,” he said, adding that the law-enforcement authorities received no complaints from 92 percent of polling stations.

Tamazian insisted that the authorities are doing their best to identify and punish those responsible for such violations. He said they might open more criminal cases in the coming days.