Up to 2.5 million votes could have been manipulated in the Turkish referendum which ended in a tight 'Yes' vote for greater presidential powers, an Austrian member of the Council of Europe observer mission, Alev Korun, told ORF radio.
"This is about the fact that actually the law only allows official voting envelopes. The highest election authority decided however - as it were, against the law -that envelopes without official stamp should be admitted," she explained.
"There is a suspicion that up to 2.5 million votes could have been manipulated," Reuters cited the Austrian member of parliament, as saying.
Korun also said that police in the majority Kurdish town of Diyarbakir hindered two of her colleagues from entering voting locations. She also pointed to videos on social media, which appear to show people voting more than once, although this still had to be proven.
"These complaints are to be taken very seriously and they are, in any case, of such an extent that they would turn around the outcome of the vote," Korun said.