On Turkey's political row with Germany, Celik said Berlin's apparent wish to suspend Turkey's European Union relations would not affect its candidacy to the bloc.
The Turkish foreign ministry urged citizens living in Germany or planning to travel there "to be cautious, taking into account the situation in Germany where they could risk xenophobic or racist treatment". Some German nationals have also been targeted. Ankara says Germany is deliberately supporting Turkish dissent, especially those who have played a role in the July 15, 2016 coup.
Chancellor Angela Merkel and other senior German politicians on Sunday dismissed a travel warning for their country issued by Turkey amid persistent tensions between the two nations.
"The relationship between Turkey and Germany must not develop in the manner that the government in Ankara is obviously and systematically pushing forward", Schulz said on the sidelines of a campaign event in the city of Mainz. "We fight for freedom of speech - in our market places and everywhere else".
In its travel advisory, Turkey told its citizens that Germany welcomes terrorist groups, such as the Kurdistan Workers' Party (PKK) and the network of the US-based Islamic cleric Fethullah Gulen. "It is worrying that a chancellor-candidate political leader in Germany has recently made statements including clear racist elements and German officials took no measures for it", it said. It also cited fires of "undetermined causes" in immigrant neighborhoods in Germany as well as alleged ill-treatment of Turkish citizens at German airports as a basis for its warning.
Lithuania's foreign minister Linas Linkevicius also turned down recent calls by German politicians to end Turkey's European Union talks, and warned that such a move could have counterproductive consequences.
About 3 million people of Turkish origin live in Germany. Germany's military is under parliamentary control and lawmakers insist they must be able to freely visit their soldiers wherever they serve.
Other strains include local German authorities' refusal earlier this year to allow rallies by Turkish politicians ahead of a referendum on the Turkish president's powers.
Turkey has declared a state of emergency following the failed military coup, in effect until October.
About 50,000 people have been jailed and about 150,000 have lost their jobs as a result of a crackdown following the coup, while scores of news outlets have been shut down.