The Rheinpfalz newspaper reported, citing Gabriel, that on Sunday night unknown people had left messages with threats on an answering machine in a dentist clinic where the minister's wife works, Sputnik reported.

"The way Erdogan does this [criticizes the minister] motivates some people to try to harass and bother my wife… When a head of state starts to act against an individual, unfortunately there are people who think they have the right to organize oppression of this individual," Gabriel was quoted as saying by the Welt newspaper.

On Saturday, Gabriel called on Ankara to abstain from meddling in the country's general elections after Erdogan called Chancellor Angela Merkel's Christian Democratic Union (CDU), the Social Democratic Party (SPD) and the Greens "enemies of Turkey" and urged ethnic Turks to vote against them in the September 24 election. Following Gabriel's statement, Erdogan lashed out at the minister, warning him to "know your limits."

The relations between Berlin and Ankara have soured in recent months after Germany banned several Turkish officials from coming into the country to campaign for Erdogan ahead of a referendum that granted him more executive powers.

Turkey's President had told German Foreign Minister to “know his limits” after Sigmar Gabriel accused the Recep Tayyip Erdogan of interfering in the his country's upcoming elections.

According to the Hurriyet Daily News, Turkish President lashed out against Foreign Minister of Germany over his remarks suggesting that Ankara was intervening in German elections, telling the top diplomat to “know his limits.”

“Now they have a foreign minister who does not know his limits. Who are you to talk to the President of Turkey? Talk to the Foreign Minister of Turkey. Know your limits. He is trying to teach us a lesson. What is your background in politics? How old are you?” Erdogan bellowed at his Justice and Development Party’s (AKP) provincial advisory council meeting in the Aegean province of Denizli.

*(Image credit: SPD Saar/ flickr)