Opponents of constitutional amendments, suggesting the country's transition from a parliamentary republic to a presidential one, are unable  to conduct a full-fledged campaign in Turkey ahead of the referendum,  Director of the OSCE Office for Democratic Institutions and Human Rights (ODIHR), Michael Georg Link told Die Welt, The DW reported.

According to him, additional obstacles are imposed for the opponents of the amendments. Some of them are intimidated, he noted, the state media characterize them as adversaries and conspirators.

Link noted that the main problem is opposition parties deputies' arrests, in particular, pro-Kurdish Peoples' Democratic Party, members of which are the main opponents of the constitutional amendments. As a result, this party cannot organize a full-fledged campaign.

According to Link, another obstacle is the restriction of freedom of assembly, demonstrations and rallies, introduced after the failed coup attempt, which took place last summer. The OSCE Representative considers that an additional problem is bias of the Turkish media and imbalance of the information provided by them. This was the result of the mass arrests of opposition journalists and the closure of a number of opposition editions.

As Link noted, 158 media outlets were closed and more than a thousand journalists remained without work since July last year.

Turkish voters will head to the polls, in a controversial referendum on April 16 that could vastly expand the powers of President Recep Tayyip Erdogan.