A French citizen imprisoned in Iran for more than 880 days has been freed as France and the rest of Europe try to pursue negotiations with Tehran over the country’s rapidly advancing nuclear programme.

The French president, Emmanuel Macron, gave no immediate details of what had led to Olivier Grondeau’s release, though it came on Nowruz, the Persian new year, when Iran has released prisoners in the past.

Grondeau was met by his family and senior officials at Paris-Beauvais airport earlier this week.

Jean-Noël Barrot, France’s minister for Europe and foreign affairs, posted a picture online of Grondeau smiling onboard what appeared to be a private jet. “We will tirelessly continue our efforts to ensure that all our compatriots still held hostage, including Cécile Kohler and Jacques Paris, are in turn released,” Barrot wrote.

Grondeau’s parents, Thérèse and Alain, speaking about the moment they learned of his release, told the Guardian they felt “huge relief that finally it was happening after years of waiting.

“We are happy to be reunited with our son. This is a great moment of joy. However, our thoughts at the moment are also with Cécile and Jacques … and their families,” they added, mentioning the other French hostages in Iran.

The US president, Donald Trump, has sent a letter to Iran’s 85-year-old supreme leader, Ayatollah Ali Khamenei, to jump-start nuclear talks. Trump is also putting pressure on Tehran over its support for Yemen’s Houthi rebels, after the US military launched an intense new campaign of airstrikes targeting the group.

In going public with his detention in January, Grondeau alluded to the politics at play in his imprisonment. “You become a human who has been stocked away indefinitely because one government is seeking to exert pressure on another,” he said.

The Iranian government did not immediately acknowledge Grondeau’s release. Such releases of westerners in Iran typically come in exchange for something. Earlier this week, Iran’s foreign ministry spokesperson Esmail Baghaei said France had arrested an Iranian woman who supported Palestinians and that Tehran was still trying to gather more details about her case.

A close friend of Grondeau’s, Tristan Bultiauw, said learning of the release was “a surreal moment”, adding: “One day you’re organising rallies to call for his release, meeting politicians, struggling with all the interviews … and then you hear that he’s released. It still feels like a dream.”

Bultiauw was looking forward to seeing his friend soon and hoped to celebrate his birthday with him next week. “I am going to Paris and we want to give him space but knowing Olivier, if he wants a big birthday party, we will all join in,” Bultiauw said. “He also got a new haircut and looks like a Viking. I love it.”

In an image of Grondeau taken on the private jet returning him to France, he had a plastic-wrapped T-shirt on his lap bearing a picture of the pop star Britney Spears, something officials did not acknowledge in welcoming his release. He put it on before disembarking and embracing his family.

Grondeau’s family said they had sent the T-shirt as a gift. “He loves Britney. But who doesn’t,” they said.

In interviews with French media after the family went public with his detention in January, Thérèse had described the former youth Scrabble champion as a fan of Beyoncé and karaoke.

Grondeau was detained by Iranian authorities in October 2022 in the city of Shiraz.

Though the exact details of what led to his arrest remain unclear, his detention began in the chaotic aftermath of the death of Mahsa Amini, a 22-year-old woman who died after being detained over not wearing Iran’s mandatory headscarf, or hijab, to the liking of authorities. UN investigators later said Iran was responsible for the “physical violence” that led to her death, which sparked months of protests and a bloody security force crackdown in the country.

“Most of the questions were: ‘Did you take part in a demonstration?’ ‘List all of the Iranians that you met during your trip,’ ‘Why did you come to Iran?’ ‘You’re not a tourist,’” Grondeau said in a phone call aired by the French broadcaster France 2 in January. “One day you think you’re going to be freed very quickly, the next you think you’ll die here,” he added.

He described lights being shone on prisoners day and night, as well as being blindfolded each time he was taken out of his cell while in solitary confinement for 72 days. He later shared a cell with more than a dozen prisoners.

Asked if he had been ill-treated, he said: “If you look for bruises on my body you won’t find any, because they are not that stupid.”

An Iranian court later sentenced the backpacker to five years in prison on espionage charges that he, his family and the French government vigorously denied.

He had been held at Tehran’s notorious Evin prison, which holds westerners, dual nationals and political prisoners often used by Tehran as bargaining chips in negotiations with the west.