Turkey has warned its citizens visiting Germany to "be careful" and guard against "far-right and racist propaganda", prompting an angry reaction from Chancellor Angela Merkel and other senior German politicians.

The incident is the latest manifestation of persistent tensions between the two nations.

The warning issued by Turkey's foreign ministry over the weekend cited increased right-wing and racist rhetoric ahead of Germany's September 24 election.

Speaking at a rally in Delbrueck, in western Germany, on Sunday, Mrs Merkel rejected the claim.

"I want to say very clearly here that every Turkish citizen can travel to us," she was reported her as saying.

"No journalists are jailed here, no journalists put in investigative custody and we have freedom of opinion and the rule of law. And we are proud of that."

Mrs Merkel's centre-left election rival Martin Shulz similarly tweeted: "Fact is: it's in Turkey, not here, that journalists who speak their opinion are jailed."

Among the reasons for strained relations between Ankara and Berlin is the refusal earlier this year by local German authorities to allow rallies by Turkish politicians ahead of a referendum on the Turkish president's powers.

In response, Turkish President Recep Tayyip Erdogan accused Germany of "committing Nazi practices".

In the build-up to the German election, Mrs Merkel and Mr Shulz have clashed over Turkey policy, but both have shown themselves unimpressed by Mr Erdogan's remarks.

Mrs Merkel has said Turkey was departing from democratic practices at "breakneck speed".

Mr Shulz has said he would seek to end Turkey's membership talks with the EU.