Turkey's Premier Recep Tayyip Erdogan was to hit the home stretch of a campaign marathon Saturday on the eve of local elections, as police hunted those behind a spate of damaging online leaks.
Erdogan and his Islamic-leaning party, after over a decade in power, face the first electoral test following months of political turmoil, with mass street protests and a corruption scandal spread via Twitter, Facebook and YouTube.
Although Erdogan's name won't be on the ballot in the mayoral and local assembly polls Sunday, he has campaigned tirelessly with multiple daily speeches to support candidates of his Justice and Development Party (AKP).
Erdogan, 60, was forced to cancel two campaign events on Friday, reportedly on doctors' orders to avoid permanent vocal chord damage, after his voice had gone hoarse and then squeaky this week.
Undeterred, the man dubbed "the sultan" by his followers was Saturday set to resume his punishing schedule with five municipal campaign events in Istanbul, the megacity of 15 million people of which he was once mayor.
A recurring theme of Erdogan's passionate speeches has been the "traitors" he blames for revealing the spate of corruption allegations since December that have claimed four ministerial scalps since.
He has charged that the graft crackdown and leaks are the work of his ally-turned-arch enemy, US-based Muslim cleric Fethullah Gulen, whose loyalists hold key positions in the Turkish police force and justice system.
In the latest YouTube leak, which the government has labelled "an act of espionage", voices at an apparent high-level security meeting are heard discussing plans to fabricate a pretext for military action in Syria.
Turkish police overnight briefly detained Onder Aytac, an author on security issues who claimed on TV before the YouTube leak that Turkey was preparing for a military operation in Syria, CNN-Turk television reported.
Aytac, a former police academy lecturer, is said to be close to the Gulen Movement.
The Erdogan government has pressured media outlets and launched an internet clampdown, including recent orders to shut Twitter and YouTube which have sparked protests from Turkey's NATO allies and human rights groups.
Amnesty International labelled the bans "a crude attempt at government censorship that will only generate deeper distrust and frustration".
"Even if the Turkish authorities have legitimate concerns about some of the content... it is completely disproportionate to enforce a blanket YouTube ban in the entire country," said Amnesty's Turkey researcher Andrew Gardner.
Writers including Salman Rushdie, Guenter Grass and Turkey's Orhan Pamuk urged the government "to remember that this beautiful country will be stronger and happier when, and if, it appreciates pluralism, diversity and the freedom of words".
Amid an atmosphere of distrust ahead of Sunday's election with over 50 million eligible voters, the main opposition Republican People's Party (CHP) and tens of thousands of citizen volunteers plan to monitor the ballot count.
For Erdogan there is much at stake as he seeks to maintain his hold on power despite the recent turmoil.
He has long had his eye on taking over from President Abdullah Gul in August elections, the first in which Turkish voters will directly elect the head of state.
Next year brings the end of Erdogan's third four-year term as prime minister, the maximum under AKP party rules, which Erdogan has however hinted he may want to change.