Turkish Prime Minister Binali Yildirim delivers a speech during an event in Oberhausen, western Germany, on February 18, 2017 | Sascha Schuermann/AFP via Getty Images Turkish PM hits campaign trail in Germany Some 1.5 million German Turks are eligible to vote in Turkey’s April referendum to expand presidential powers.

Turkish Prime Minister Binali Yildirim took a detour on his visit to Germany on Saturday to stump for German Turkish votes for the April constitutional referendum.

Addressing thousands of Turks gathered in the arena of Oberhausen, a city in western Germany, Yildirim told supporters that if they love their country, they have to vote yes.

During his speech the Prime Minister also attacked Fethullah Gülen, the 75-year-old Islamic cleric who lives in self-imposed exile in the U.S. since the 1990s and is accused by Ankara of masterminding July’s coup attempt.

He told the crowd that all members of “FETÖ” — an abbreviation for “Pro-Fethullah Terror Organization" — hiding in Turkey or anywhere in the world, will be found and punished, according to Turkish newswire Anadolu Agency.

The event was private and several German journalists were denied access during the speech despite having been granted accreditation ahead of time.

The proposed reform will expand the powers of President Recep Tayyip Erdoğan. Having a Turkish politician campaign in a foreign land for a local reform is not uncommon in Germany, which currently is home to the world's biggest Turkish diaspora community, and where nearly 1.5 million Turks are eligible to vote in the referendum.

The gathering has come under fire in Germany following the detention of a correspondent for German newspaper Die Welt on Friday.

"If well advised Mr Yildirim should rather ensure the liberation of the journalist," Rolf Mützenich a German MP from the Social Democrats, told the local paper "Kölner Stadt-Anzeiger."

Cem Özdemir of the Green Party told Deutsche Welle that Yildirim is "campaigning for a state at Erdogan's mercy," while Left Party politician Sevim Dagdelen said Yildirim should be denied entry in order to prevent this "ad campaign for a Turkish dictatorship."

While supporters of Erdogan were singing inside the arena, those opposed to the referendum gathered outside to protest the Turkish president's growing authoritarianism.