Turkish police detained at least 80 people who are known to have been involved in activities to endorse a “No” vote in the upcoming presidential referendum, according to Transparency International’s (TI) Turkey branch.

TI Turkey said it will monitor the incidents of right abuse and unlawful government actions in the run up to the referendum and share the results with public in regularly released reports.

In the first of such reports, TI Turkey said over 80 people were detained while they were campaigning for a “No” vote on between Dec. 25 and Jan. 31.

The report underlines that the reason for most of the detainments was recorded as “to distribute leaflets against the constitutional change.”

The referendum is set to introduce a shift from parliamentary power to the executive presidency which will give more power to President Recep Tayyip Erdoğan.