Iran has warned of a "proportionate and "firm" response after Germany said the European Union was seeking new sanctions against the country over its deadly crackdown on protests.

 "A provocative, interventionist and undiplomatic stance does not show sophistication and wisdom," Iranian Foreign Minister Hossein Amir-Abdollahian tweeted.

 "The undermining of old ties has long-term consequences. Germany can choose cooperation to solve common problems or confrontation. Our response will be proportionate and firm," he added, without going into details.

 German Foreign Minister Annalena Berbock said on Wednesday that the European Union is "working hard on the next package of sanctions" against Iran in response to the crackdown on protests sparked by the death of Mahsa Amini.

 "We will not give up," she wrote on Twitter. "We will support the men and women of Iran not only today, but for as long as it takes."

 EU foreign ministers are to meet on Monday in Brussels.