The final day of campaigning is taking place in Turkey ahead of a referendum on whether to grant sweeping new powers to the president, BBC News reports.

President Recep Tayyip Erdogan is seeking to replace the parliamentary system with an executive presidency. Approval could see him stay in office until 2029.

Supporters say a "yes" vote would streamline and modernise the country; opponents fear the move would lead to increasingly authoritarian rule.

The referendum could bring about the biggest change to the governing system since the modern republic was founded almost a century ago.

It also takes place under a state of emergency which was imposed following a failed coup last July. A government crackdown since then has seen tens of thousands of people arrested.

President Erdogan is holding his final rally in Istanbul and says he is confident of victory.

He assumed the presidency, a largely ceremonial position, in 2014 after more than a decade as prime minister.

The referendum on constitutional change would abolish the post of PM, allowing the president to appoint cabinet ministers and bring all state bureaucracy under his control.

The president says the new system will resemble those in France and the U.S. and will bring stability in a time of turmoil marked by a Kurdish insurgency, Islamist militancy and conflict in neighbouring Syria that has led to a huge refugee influx.