President Erdogan signed off on the reform bill on Friday, clearing the way for a national referendum on major constitutional changes that would usher in a powerful presidency.

Deputy Prime Minister Numan Kurtulmus said that the referendum "is planned to take place on April 16." However the election board has yet to officially announce the date.

Constitutional overhaul

Erdogan says the reforms will provide stability, efficiency and prevent a return to fragile parliamentary coalitions of the past.

Critics, however, fear the changes will significantly weaken Turkey's checks and balances, leading to increasingly authoritarian rule.

Turkey's parliament approved the reform package in contentious and sometimes violently debated sessions last month. A majority of lawmakers supported the bill in the assembly, but the measures failed to clear the threshold required to come into force without a public vote.

The new 18-article constitution would create an executive presidency similar to the system in the United States and France. Currently, the office of the presidency is a largely ceremonial position.

The changes would scrap the office of prime minister - currently Turkey's head of government, and a position Erdogan held for a decade before becoming president. It would also grant the head of state the power to hire and fire ministers, and could allow Erdogan to remain in office until 2029.

The post of prime minister would be replaced with one or several vice presidents.

Campaign challenges

Campaigning for the referendum will take place under a state-of-emergency that has been in place since a failed coup attempt last July. Opposition supporters say the conditions could significantly hamper their efforts to rally against the constitutional reforms.

Since the coup attempt, the Turkish government has shuttered dozens of opposition and critical media outlets and placed over 120 journalists still in jail. Of the countries where reliable records exist, Turkey is the world's most prolific jailer of journalists.

Erdogan signed an executive order this week that removes the powers of the election commission to impose fines on private broadcasters who violate impartiality rules during campaigns.

rs/msh (AP, AFP, dpa, Reuters)