Turkey’s recent travel advisory warning citizens of xenophobia and racism in Germany is a “bad joke,” offending the country’s dignity, Chancellor Angela Merkel’s chief of staff said amid the heated spat between the two NATO allies.

“Turkey’s travel warning against Germany is a bad joke!” Peter Altmaier, head of Merkel’s chancellery office, wrote on Sunday in an emotional tweet.

“Baseless imprisonment for many Germans is unjust! Nazi comparisons offend our honour!” he said, referring to previous exchanges between Ankara and Berlin, in which Turkish President Recep Tayyip Erdogan repeatedly accused the German government of employing “Nazi practices.”

Reisewarnung der Türkei gegen D ist ein schlechter Witz!Grundlose Haft für viele Deutsche ist Unrecht!Nazivergleiche verletzen unsere Ehre! — Peter Altmaier (@peteraltmaier) September 10, 2017

On Saturday, the Turkish Foreign Ministry warned citizens to “be careful” and keep their composure in the face of “racist and xenophobic slurs.”

“It is advised for our citizens in Germany or planning to visit this country to be even-tempered, keep themselves out of political discussions and absent themselves from rallies held by terrorist groups ahead of the elections,” the ministry said on its website.

The travel advisory also accused German leaders of employing “anti-Turkish rhetoric” in their election campaigns, and of blocking Turkey’s accession into the EU.

Terrorists “walk freely on the streets” in Germany, the foreign ministry alleged. It also claimed that Turks were being ill-treated at German airports and that racially-motivated arsonists had assaulted Turkish-populated neighborhoods.

READ MORE: ‘Who are you? Know your limits!’ Erdogan attacks German FM in elections interference row

Chancellor Angela Merkel expressed unease over the Turkish travel warning. “I want to be very clear here: Any Turkish citizen can come visit us,” the chancellor said during a campaign rally in Delbrueck, according to Deutsche Welle.

“No journalists are arrested here. No journalists are put into detention here. Here, we have freedom of expression and the rule of law. And we’re proud of that,” Merkel added.

Peter Tauber, Secretary General of Merkel’s CDU party, tweeted: “Is Erdogan warning about traveling to Germany so that the people there don’t see how freedom, justice and open-mindedness make a country strong?”

Warnt Erdogan vor Reisen nach Deutschland, damit die Menschen dort nicht sehen, wie Freiheit, Recht und Weltoffenheit ein Land stark machen? — Peter Tauber (@petertauber) September 9, 2017

The rift between the two countries has been deepening over the past months. Following the failed 2016 military coup attempt in Turkey, Ankara accused Berlin of harboring supporters of US-based cleric Fethullah Gulen, who was named by Erdogan as the mastermind behind the coup.

Germany has repeatedly accused Turkey of disrespecting human rights, demanding the release of German citizens detained by Ankara over alleged “terrorism support” and participation in the coup attempt.

Berlin has also pulled out its troops and combat aircraft from Turkey’s Incirlik Air Base amid the political row. Previously, Berlin recognized the early 20th century Armenian massacre in the Ottoman Empire as “genocide.”

In early September, two Germans were detained in Turkey. According to the German Foreign Office, “the arrests could be politically motivated,” Deutsche Welle reported. Steffen Seibert, spokesman for the chancellor, warned that Germany expects “German citizens who are imprisoned for incomprehensible reasons, be released.”