The EU co-ordinator of the Iran nuclear talks has hit out at German authorities after he was detained at Frankfurt airport on his way back from Tehran.
Enrique Mora said the incident happened on Friday morning when he was connecting to a flight to Brussels.
Writing on Twitter, the Spanish diplomat said he had received “not a single explanation” from German authorities regarding his treatment.
“An EU official on an official mission holding a Spanish diplomatic passport. Took out my passport and my phones,” he wrote.
Mr Mora said the EU Ambassador to the UN in Vienna and the head of the EU’s Iran task force were also detained.
“We were kept separated,” he wrote. “Refusal to give any explanation for what seems a violation of the Vienna Convention.”
Neither German police nor Germany’s foreign ministry responded immediately to requests for comment.
His visit to Tehran raised hopes of a revival of the Iran nuclear deal, with Josep Borrell, the EU's top diplomat, saying negotiations had been “unblocked”.
Mr Mora met Iranian Deputy Vice President Ali Bagheri in Tehran for what was described as a “last bullet” push for an agreement.
Speaking on Friday, Mr Borrell said Iran's response had been “positive enough” after Mr Mora had delivered a message that things could not continue as they were.
“These things cannot be resolved overnight,” Mr Borrell told reporters at a G7 meeting in northern Germany.
“Let's say the negotiations were blocked and they have been unblocked and that means there is the prospective of reaching a final agreement.”
Talks to revive the landmark agreement between Iran and world powers have been on hold since March, mainly due to Tehran’s insistence that Washington remove the Islamic Revolutionary Guard Corps from its list of terrorist groups.
There is little chance of the US agreeing to remove Iran's elite security force from its list of foreign terrorist organisations any time soon, a French diplomatic source said on Thursday, casting a further pall over nuclear negotiations.
Former US president Donald Trump pulled the US out of the 2015 Joint Comprehensive Plan of Action accord in May 2018, fulfilling a key pledge of his campaign.