Erdogan wants to change the Turkish constitution to turn the ceremonial role of president into that of a chief executive, a Turkish version of the system in the United States, France or Russia.

Asked on his return from a visit to Saudi Arabia late on Thursday whether an executive presidential system was possible while maintaining the unitary structure of the state, he said: "There are already examples in the world. You can see it when you look at Hitler's Germany.

"There are later examples in various other countries," he told reporters, according to a recording broadcast by the Dogan news agency.

A Turkish official told Reuters the comments had been taken out of context.

"There are good and poor examples of presidential systems and the important thing is to put checks and balances in place," the official said.

"Nazi Germany, lacking proper institutional arrangements, was obviously one of the most disgraceful examples in history."

The ruling AK Party, founded by Erdogan, has put a new constitution at the heart of its agenda after winning back a majority in a November parliamentary election.