Turkey's ruling party has formally launched a campaign urging a yes vote in a referendum to amend the constitution, eliminating the position of prime minister and extending the powers of the president.

Prime Minister Binali Yildirim waved and threw flowers to his supporters, among an estimated 40,000 flag-waving members of the Justice and Development Party in Ankara on Saturday, to push for the approval of the bill on April 16.

"For a strong Turkey, lasting stability, our choice is 'yes'. This is our wish, it will come," said Yildirim.

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Al Jazeera's Paul Brennan, reporting from Turkey's capital, said the party, known by its Turkish acronym AKP, was trying to project unity amid political divisions in the country.

But the "irony" of Yildirim's position is that he will be strongly arguing for the abolition of his own post, Brennan said.

The referendum comes less than a year after a failed coup attempt against the government of President Recep Tayyip Erdogan.

Erdogan has said the changes will prevent a return to fragile parliamentary coalitions of the past, and provide stability at a time of turmoil.

There have been 140,000 people arrested, detained or suspended from public sector posts since the coup attempt failed in July 2016.

Test of patriotism

Erdogan also called the vote a test of patriotism. He has referred to voters opposing the bill as "terrorists".

But critics fear a slide towards what they call authoritarianism.

Al Jazeera's Brennan said there are "concerns that too much power rests with the president."

He said the main challenge for Erdogan and his allies was to assure voters "that there are safeguards put into the proposal" to make sure the president does not wield too much power.

If the changes are passed in the referendum, Turkey would head to general and presidential elections in November 2019 - and the proposed powers would be granted to whoever is elected president.

The bill indicates a person can be elected president for two five-year terms.

Erdogan's existing time as president will not be counted, meaning that, if the legislation is approved, he could stay in office until 2029.