The people of mainly Muslim Tajikistan are voting on a ban of religion-based parties, in a poll likely to strengthen the president’s power.
Emomali Rakhmon has ruled the ex-Soviet Central Asian republic since 1992, surviving a civil war which ended in a deal with the Islamist opposition.
Moves to ban the opposition Islamic Renaissance Party began last year.
Sunday’s referendum also asks voters to lift limits on the number of terms a president can serve in the office.
It further proposes lowering the age limit for running for president from 30 to 35 years of age.
The three points are contained in a parliamentary bill on amendments to the constitution.
The single question on the ballot form was “Do you support the amendments and additions to the constitution of the country?”
Since the power-sharing agreement that ended the civil war in 1997, Islamists have been gradually pushed out of the government.