Turkey's state-run news agency says 49 people with alleged links to the Islamic State group have been detained for planning "sensational attacks" in the run-up to Sunday's referendum on increasing the powers of the president. The referendum is seen by many as the ultimate test of President Recep Tayyip Erdogan's popularity.
Cabinet ministers would no longer have to be members of Parliament and the Parliament would not have power over Cabinet appointments - ministers would be appointed directly by the president.
If passed, the new presidential system will implement the most radical political shake-up since the fall of the Ottoman Empire, dispensing with the office of the prime minister and centralising the entire executive bureaucracy under the presidency.
Immediately after the putsch, a state of emergency was declared, and the Justice and Development Party (AKP) government along with President Recep Tayyip Erdoğan pinned the blame on the Gülen movement. The reformed constitution would give Erdogan the power to make government appointments, take back the leadership of the ruling party, and stay in power until 2029, pending presidential and general elections in 2019, with a maximum of two five-year terms.
More than 55 million people are eligible to vote at 167,140 polling stations across the country, according to Reuters.
Despite the stability President Erdogan is offering, he says he does not support giving him dictator-like authority.
The constitutional changes proposed in the referendum would consolidate power in his hands. If the president dissolves parliament, then both parliamentary and presidential elections will be renewed.More news: Mark Hamill: Carrie Fisher Star Wars tribute is 'therapy'
The ruling AKP argues that bestowing power on the presidency would strengthen the country's governance.
For Erdogan, 63, a presidential system has been a long-time dream.
Other changes would see the minimum age for parliamentary candidates reduced to 18 and the number of deputies rise to 600.
The majority of the "Yes" voters who I talked to in various districts of the 15-million megapolis said the fact that Erdogan and his party improved their living standards immensely is the main factor determining the colour of their vote.
The referendum comes amid troubled times for Turkey, which has been plagued by a string of bombings, renewed violence between the government forces and Kurdish rebels and a failed coup attempt in July that resulted in a state of emergency that remains in place.
The opposition has complained of a lopsided campaign, with Erdogan using the full resources of the state and the governing party to dominate the airwaves and blanket the country with "yes" campaign posters. He also appealed to voters of other parties to approve the changes so "Turkey can leap into the future". One of the government's emergency decrees abolished sanctions against media organisations producing biased coverage in the lead up to the election, to the obvious benefit of the government, which now indirectly controls the bulk of Turkey's media.
The referendum is taking place after a bloody year of terror attacks in Turkey blamed on jihadists and Kurdish militants.
Security will be high for Sunday's vote, with almost 34,000 police deployed in Istanbul alone.