Turkish President Recep Tayyip Erdogan on Friday warned the European Union he would sign a law bringing back the death penalty if it was approved by parliament.

"Democracy, it's respecting the people's will," Erdogan said in a speech in Istanbul, recently.

"If the people say 'we want the death penalty'... and this goes to parliament and parliament passes it and it comes to me, I declare I will approve this," he added.

Erdogan was speaking hours after he had rattled Europe by threatening to open Turkey's borders to allow migrants to reach the EU, in a move that would tear up a landmark deal signed in March that has reduced the refugee flow.

He made his remarks in response to the cheering crowds' chants of "we want the death penalty", an oft-repeated call during his rallies since the July 15 failed coup.

"When you want the death penalty, the gentlemen are uncomfortable," he said, apparently referring to EU officials.

Erdogan said that if he signed the death penalty back into law, it would likely be blocked by the European Court of Human Rights (ECHR), but this did not concern him.

"I say, it doesn't bother me. Because the European Court of Human Rights gives a lot of decisions, we know it very well... this people's will, yes this is a will that must be respected by everyone."

EU officials have repeatedly made clear that bringing back the death penalty would end Turkey's bid for membership, which sets abolishing capital punishment as a condition.

Turkey completely abolished the death penalty in 2004 as part of its accession process.

The move meant the 1999 death sentence for Kurdish separatist leader Abdullah Ocalan was commuted to life behind bars.

No judicial executions have taken place in the country since left-wing militant Hidir Aslan was hanged on October 25, 1984 in the wake of the 1980 military coup.