Two US pollsters commissioned by Georgian opposition forces called into question official results that showed the governing Georgian Dream party won last weekend’s parliamentary election in the South Caucasus country, as opposition parties prepared to hold a new protest next week, Reuters reports.

US data and polling firm Edison Research, commissioned by the pro-opposition television channel Formula, said the differences between its own exit poll and the official results pointed to “manipulation” of the vote.

HarrisX, another US pollster that ran an exit poll for pro-opposition television channel Mtavari Arkhi, said the official results were “statistically impossible”.

Widely seen as pivotal for the former Soviet republic, the election offered a choice between further European integration under the pro-Western opposition, or closer ties with Moscow under a governing party that critics say is increasingly authoritarian.

Observer groups, including the 57-nation Organization for Security and Co-operation in Europe, have said violations such as ballot-stuffing, voter intimidation and bribery could have swayed the election, but stopped short of saying it was outright stolen. Russia has denied interfering in the election.