A Spanish man trekking from Madrid to Qatar for the 2022 Fifa World Cup in Doha is believed to be under arrest in Iran where he went missing more than three weeks ago, his family have said.

Santiago Sanchez’s mother, Celia Cogedor, told the Associated Press on Wednesday: “We learned this morning from the (Spanish) foreign ministry that there’s a 99% chance he is arrested.

“We are filled with hope.”

Mr Sanchez’s sister is due to meet officials at the Spanish Foreign Ministry in Madrid on Thursday to learn further details.

The ministry said in a statement that the Spanish embassy in Tehran is in touch with Iranian authorities about 41-year-old Mr Sanchez. It declined to provide further details.

Iran is being engulfed by mass unrest, triggering fears about Mr Sanchez’s fate after he stopped contacting his family in Spain on October 2, a day after he crossed the Iraq-Iran border. He had warned his family that communication might be difficult in Iran.

The Spanish adventurer planned to go to Tehran, the Iranian capital, where a television station wanted to interview him.

His next destination would have been Bandar Abbas, a port in southern Iran where he would board a boat to Qatar. But all traces of him vanished even before he reached Tehran, his parents said.

His family reported him missing on October 17 and said they are being supported by Spanish police and diplomats.

This was not Mr Sanchez’s first time in Iran. In 2019 the avid football fan cycled a similar route to get from Madrid to Saudi Arabia.

His parents said they are proud of his adventurous spirit and that his only aims are to help others and promote the Real Madrid team.

Mr Sanchez’s disappearance in Iran came as protesters are rising up across the Islamic Republic in the largest anti-government movement in more than a decade.

The demonstrations erupted on September 16 over the death of Mahsa Amini, a 22-year-old woman taken into custody by Iran’s morality police for allegedly not adhering to the country’s strict Islamic dress code.

Tehran has violently cracked down on protesters and blamed foreign enemies and Kurdish groups in Iraq for fomenting the unrest, without offering evidence.

The Iranian Intelligence Ministry said authorities have arrested nine foreigners, mostly Europeans, over their alleged links to the protests.