Since US President Donald Trump quit the agreement in May last year, the European Union has repeatedly renewed its own commitment and pledged to reward Iran's compliance with the sanctions relief promised under the deal.

But its failure to find an effective mechanism to enable its firms to continue doing business following the reimposition of US sanctions has left Tehran increasingly frustrated.

And strong criticism by the EU last month of Iran's decision to retaliate by declaring itself no longer bound by some of its commitments has sparked further anger.

The ultra-conservative Javan newspaper ran a front-page cartoon depicting Foreign Minister Heiko Maas wearing a swastika armband, sporting a toothbrush moustache and performing a Nazi salute.

"The stinking leftovers of Nazism and fascism have manifested themselves in the spirit of the weakest Europe in history," it said in an accompanying editorial.

The European Union "sent its envoy to Iran to say 'Europe cannot implement without America's approval but cannot accept Iran's refusal to deliver on some of its commitments'", the paper complained.

Leading ultraconservative daily Kayhan recalled the involvement of German firms in providing materials used by Saddam Hussein's regime to develop weapons of mass destruction it deployed in the 1980-88 Iran-Iraq war.

"Germany, as one of the main suppliers of weapons of mass destruction to Saddam ... should have apologised to Iran and reconsidered its policy instead of expressing concern over Iran's defensive capabilities," it said.

Since 2015, Iran has continued developing and testing ballistic missiles, which it says are for defensive purposes only and completely within the term of the nuclear deal.

But the EU has echoed US criticism of the tests and has called for restraint from Tehran.

The conservative Resalat newspaper mocked Europe's repeated promises to rescue the nuclear agreement, saying "the powerless cannot perform miracles."

During his visit on Monday, Maas acknowledged that the economic benefits Tehran hoped for from the nuclear deal were now "more difficult to obtain" but urged Iran to fully respect the agreement.

It is in Iran's "political and strategic interest to maintain this agreement and the dialogue with Europe", he said.