Turkish President Recep Tayyip Erdogan on Sunday called on Turkish-origin Germans to give a “slap” to both parties in Chancellor Angela Merkel’s ruling coalition in September polls, pressing on with what Berlin has condemned as unprecedented meddling.

Erdogan has caused consternation in Berlin by urging ethnic Turks in Germany to vote neither for Merkel’s Christian Democratic Union (CDU), its coalition partner the Social Democratic Party (SPD) nor the Greens in the Sept. 24 legislative polls.

Defiantly returning to the controversy for the third consecutive day, Erdogan called on ethnic Turks living in Germany not to vote for parties who are “enemies of Turkey.”

“Be with those who are friendly to Turkey. Don’t worry if it’s a small party, give them your vote. They will then grow and get bigger.”

“In my opinion, those who attack Turkey in this way need to be dealt a slap in this election,” Erdogan told ruling party activists in a televised speech in Istanbul.

He did not specify which parties the Turkish community in Germany should consider voting for.

Foreign Minister Sigmar Gabriel, a senior member of the SPD, had bitterly denounced Erdogan’s calls as an “unprecedented act of interference” in Germany’s sovereignty.

This prompted the Turkish president the day earlier to tell Berlin’s top diplomat to “know your limits” and question his political experience. And Erdogan on Sunday brushed off the criticism that he was meddling in the elections. “What are they saying now? They are saying ‘he’s interfering in our democracy.’ But all we are saying is that our citizens should give the enemies of Turkey a lesson at the ballot box. That’s all.”

The latest spat between Ankara and Berlin risks propelling a months-long crisis in ties between two NATO allies with deep historic links to a new level.

Berlin has lambasted Ankara over the magnitude of the crackdown that followed last year’s failed coup, which has seen several German citizens arrested, including journalists.

Ankara, meanwhile, has accused Berlin of failing to extradite suspected Kurdish militants and coup plotters who have taken refuge in Germany. Analysts estimate that about 1.2 million people of Turkish origin will have the right to vote in the September elections.

Meanwhile, Austria has joined Germany in its criticism of the Turkish president.

Austria’s Foreign Minister Sebastian Kurz entered the fray on Sunday, criticizing Erdogan in an interview with newspaper Die Welt am Sonntag. Kurz, who is running for Chancellor in October’s election, accused Erdogan of trying to rile up the Turkish diaspora.

“President Erdogan is trying to instrumentalize ethnic Turkish communities, especially in Germany and Austria,” he told the paper. “He polarizes and brings Turkish conflicts into the EU.

“I condemn the constant interference by Erdogan in the internal affairs of other states — and it’s not happening only in Germany.”

-Agencies