Turkish President Recep Tayyip Erdogan said he would "rip the heads" off traitors and spoke in support of reinstating the death penalty, as hundreds of thousands of citizens gathered to mark the anniversary of a failed coup.

Speaking to a crowd gathered on the bridge in Istanbul where civilians clashed with tanks and soldiers on the night of the putsch last year, Mr Erdogan also said those put on trial should be made to wear outfits similar to detainees at the United States' most notorious military prison.

“I have spoken with our prime minister and said 'when they appear in court, they should wear one type of outfit, like in Guantanamo," Mr Erdogan said to cheers.

Two hundred and forty nine people, not including the plotters, were killed when a disgruntled faction of the army sent tanks into the streets and war planes into the sky on July 15 in a bid to overthrow Erdogan after one-and-a-half decades in power.