Sweden has demanded the immediate release of an EU diplomat who has been held in an Iranian jail for more than 600 days and is facing trial on charges of spying for Israel. Ulf Kristersson, the Swedish prime minister, said on Monday that intensive work was under way to try to free Johan Floderus from Tehran’s Evin prison after Iran said on Sunday that a trial of the Swedish national had begun. Floderus is charged with spying for Israel and “corruption on Earth”, a crime that carries the death penalty. Kristersson said the charges against the 33-year-old, who was arrested in Iran in 2022, were “completely without factual basis” – a conclusion that both the Swedish government and the European External Action Service, the EU’s diplomatic service, had reached. “We demand his immediate release,” Kristersson said in a press conference in Stockholm. “We have very intensive work we are showing Iran on this issue. But I will not be going into anything of the contents of that work.” He added: “We are also in close contact with his family.” Floderus’s employers at the European Commission in Brussels reiterated their call for his release and said they were seeking more information about the latest developments. “We have been extremely clear from the beginning that Mr Floderus is innocent. There are absolutely no grounds for keeping Johan in detention,” an official spokesperson said. They said the EU chief diplomat, Josep Borrell, at whose department Floderus worked, continued to call for his liberation. “We are seeking clarification and more information from them in close coordination with the Swedish authorities who bear the consular responsibility. The European Union will continue to work tirelessly to secure the release of our colleague Johan and that of other EU nationals … who are arbitrarily detained,” she added. Last week, Floderus’s father, Matts Floderus, revealed the “levels of hell” his son had experienced as Friday marked 600 days of incarceration with no routine consular visits or phone calls. His father told the Guardian that his son had been on hunger strike at least five times and that he was sharing a cell with no bed in it and slept under 24-hour lighting. Appealing for his son to be freed, Floderus said his wife hoped he would be home for Christmas. “It is devastating for her. There are moments it is very difficult for both of us. We have both cried a lot, she a lot more than me. But I have also cried more than I have done since I was maybe two or three years old,” he said. “We are deeply worried and say this over and over again. He has been arbitrarily detained. He has done nothing wrong and should be freed and allowed to leave the country.”