A "warped mentality" and double standards in the fight against terrorism. These were the charges levelled at Germany by the Turkish ministry of foreign affairs in its response to the publication of a leaked internal German government assessment that in turn described Turkey as a leading hub for Islamist groups.

A diplomatic spat has emerged between Turkey and Germany over the leaked documents, which highlighted allegations that the Turkish authorities have undergone "Islamization."

"The claims that appear in news reported by the German State TV channel ARD in relation to a German Intelligence Service report are a new indicator of the warped mentality that for some time now has been aimed at wearing down our country, our honorable president, and our government," the Turkish ministry of foreign affairs said in a statement.

"Behind theses claims, there are some political circles in Germany known for their double standards in the fight against terrorism, including against the PKK terrorist organization's bloody actions that continue to target Turkey."

From bad to worse

The spat is bad news for hopes of turning back the deterioration in relations between Ankara and Berlin, at least in the short term, says Professor Ayhan Kaya of Istanbul Bilgi University.

"It is becoming more and more difficult to restore the relations between Turkey and the EU in general and Turkey and Germany in particular," Kaya told DW.

"What is certain is that both sides are losing their mutual trust. However, German-Turkish relations have very strong historical fundamentals, and both sides will eventually find ways to restore the relations."

The internal German government document that prompted the spat was leaked to ARD on Tuesday.

"As a result of the increasing Islamization of Ankara's domestic and foreign policy since 2011, Turkey has become a central platform for action for Islamist groupings," the document said.

"The many expressions of solidarity and acts of support for the Egyptian Muslim Brotherhood, Hamas and armed Islamist opposition groups in Syria by the governing Justice and Development Party and President Erdogan underline their ideological affinity."

Creeping 'Islamization'

The charge of "Islamization" is at least partly correct, says Timur Kuran, professor of economics, political science, and Islamic studies at Duke University.

"Not only have Turkey's politics been Islamicized through AKP's deliberate policies, but Turkey's very large secular minority is under pressure to accept more and more religion in public life."

Kuran points to the strong support the country's mosques provided to the government during the failed coup attempt as an example of this.

"Never since 1923 has Islam been so central to the government's policies," he told DW.

Relations between Germany and Turkey were already strained prior to the leak over disagreements between the two countries in the wake of a failed military coup that took place in Turkey in July.

A post-coup crackdown, including the imposition of a state of emergency, have drawn criticism from Europe of the Turkish authorities' conduct.

"The Turkish government and the Turkish public are now used to snubs from Europe in general and Germany in particular. It is well understood that Germany disapproves of Turkey's increasingly authoritarian regime and of the ongoing witch hunt for Gulenists," Kuran said.

Insufficient solidarity

In Turkey, a perception of a lacklustre response to the coup from Europe has spread, with many Turks feeling European leaders have expressed insufficient solidarity with the Turkish government after the military coup attempt.

More than 35,000 people have been detained in Turkey since the failed military coup, with 17,700 of those formally arrested, according to the Turkish authorities.

On Tuesday, the justice ministry announced that 38,000 prisoners, convicted before last month's coup attempt, would be eligible for conditional release after a change in the law, prompting speculation that prisons have been strained by the number of detentions and arrests.

The spat could carry risks to key agreements between Turkey and the EU. President Erdogan has repeatedly warned that if a visa deal falls through there will be a "showdown" between Turkey and the EU.

"The visa liberalization and readmission are very important. The process is currently ongoing. Unfortunately, Europe has failed to keep its promise on the issue," Erdogan told Germany's RTL television last week.

Erdogan said explicitly that should the visa deal fall through, the migrant deal would be suspended. "We want to take steps simultaneously. If it happens, fine. If not, I'm sorry but we'll stop the readmissions," he said.

However Professor Kaya of Istanbul Bilgi University says the refugee deal may not necessarily be affected.

"I don't really think that this may have an impact on the refugee deal," he said. "I strongly believe that Germany and the EU should go on counting on the civil society in Turkey, which has a very strong potential to change things, as always."