Turkey will hold a series of events on Saturday to celebrate the first anniversary of the defeat of last year's failed coup attempt, as it sacked thousands of officials in the latest crackdown.

Ankara has declared July 15 - the day of the failed coup attempt - an annual national holiday of "democracy and unity", billing the foiling of the putsch as a historic victory of Turkish democracy.

At least 249 people, not including the plotters, were killed when a faction in the army sent tanks into the streets and war planes into the sky in a violent bid to overthrow President Recep Tayyip Erdogan.

From now on, nothing will be as it was before July 15 Recep Tayyip Erdogan, Turkish president

But they were thwarted within hours as the authorities regrouped and people poured into the streets in support of Erdogan, who blamed followers of his former ally, the US-based preacher Fethullah Gulen, who denies involvement.

A state of emergency imposed in the wake of the failed coup still remains in place.

At least 50,000 people have been arrested and more than 100,000 have been dismissed from services over the past year.

The scale of Saturday's nationwide commemorations is aimed at etching July 15, 2016 into the minds of Turks as a key date in the history of the modern state founded in 1923 out of the ruins of the Ottoman Empire.

"From now on, nothing will be as it was before July 15," Erdogan, whose powers have since expanded in an April referendum, said in a speech on Thursday.

He compared the defeat of the coup to the World War I 1915 Battle of Gallipoli where Ottoman troops famously withstood an onslaught by invading Allied soldiers in what became one of the founding narratives of the modern state.

"States and nations have critical turning points in their histories that shape their future. July 15 is such a date for the Republic of Turkey," he added.

READ MORE: All you need to know about Turkey's failed coup attempt

Giant posters have sprung up across billboards in Istanbul showing paintings that portray the key events of the failed coup night, including the surrender of the putschist soldiers.

A special session of parliament at 10:00 GMT starts the commemorations.

Erdogan, at the centre of the events, will then fly to Istanbul to take part in a people's march on the bridge across the Bosphorus that saw bloody fighting a year ago.

The bridge has since been renamed Bridge of the Martyrs of July 15.

At midnight local time (21:00 GMT) people across Turkey will take part in "democracy watches", rallies commemorating how people poured out into the streets.

Erdogan will then return to Ankara and at 23:00 GMT give a speech in Parliament to mark the time it was bombed.

A monument to those killed will then be unveiled outside the presidential palace in the capital as the dawn call to prayer rings out.