The dissident father of the Manchester Arena bomber, who was arrested in Libya the day after the blast alongside his other terrorist son, was quietly released without charge and has vanished.

Ramadan Abedi, 54, fought against the Gaddafi regime in Libya with a militant group that was designated a terrorist organisation by the US. After his arrest, he and his son Hashem were held by the Rada Special Deterrence Force, the most powerful of Tripoli’s militias, at its base at Mitiga airport with dozens of other terrorist suspects and fighters.

As the jail was repeatedly attacked by rival militias trying to free members held there, the British focused on bringing Hashem Abedi, 22, back to the UK to face charges in relation to the bombing. He was eventually extradited last year, but Ramadan was released without charge and disappeared.

“We don’t know [where he is], nobody is speaking about it,” said Abdel al-Fattah, the director of the foreign media office of Libya’s UN-backed government. “Even the local media don’t speak about him.”

There is no mention of him on Libyan social media and a British diplomatic source said the UK had no contact with the dual Libyan-British national.

When the Guardian contacted Kerea Tabbal, Ramadan’s mother-in-law and the brothers’ maternal grandmother at her home in Libya, she refused to confirm any details about his location. She responded angrily to being called, saying: “I am an old woman, don’t you have any shame?”

Former editor of the English-language Libya Herald newspaper Michel Cousins said Ramadan Abedi had no public profile in Libya prior to the Manchester bombing and his vanishing from sight after release excited no curiosity: “He’s not important as far as Libyans are concerned, they don’t want to know about it (the trial), its embarrassing. There are only two issues in Libya, the conflict east against west, and coronavirus.”

Hashem Abedi was transferred to Britain in July 2019 after both militia and government agreed to the UK request, but there was no news of Ramadan, with a British source saying only that he was no longer being held in jail.

The veteran of the Libyan Islamic Fighting Group (LIFG), an Islamist guerrilla organisation that battled Gaddafi’s forces in the 1990s, first arrived in Britain in 1994. When the LIFG was defeated, many veterans fled to Afghanistan and Iraq, several becoming prominent members of al-Qaida.

Initially Ramadan went to Saudi Arabia, but it is understood the Saudis persuaded Britain to take him in during a period when the two countries were negotiating the Al-Yamamah arms deal.

In Manchester, Ramadan, a security officer, was popular among some Libyan exiles, being assigned the role of muezzin at Didsbury mosque and calling out prayer five times a day.

He and his wife, Samia, lived in south Manchester for more than a decade. All of their children were enrolled in schools and the family were said to be settled.

However, some Manchester Libyans began to object to his radical style. “We call them the Abus, because they all adopt these kunyas, these nicknames, its like ‘comrade’, an alias,” said one British-Libyan resident. “There is tension, a lot of Libyans in Manchester, they don’t want to be associated with them.”

In 2011, Ramadan decided to travel back to his north African homeland to fight in the civil war, also referred to as the Libyan revolution, once again with the LIFG. The US state department says elements of the LIFG were aligned with Osama bin Laden and al-Qaida and it designated the group a foreign terrorist organisation in 2004. The armed conflict between forces loyal to Gaddafi and those seeking to oust his government lasted for eight months, but Ramadan was never to make the UK his home again.

Fellow LIFG fighter Akram Ramadan, 49, previously told the Guardian that Ramadan was passionate about overthrowing a regime that had “displaced thousands of his brethren … It was something we all felt we had to do. Some were more radical than others but we all shared a common cause.

“I saw Ramadan in the mountains and later in Tripoli. We were all soldiers – we all bore arms. It was a war zone. Many of the people who fought in the conflict weren’t actually born in Libya, but they had this common cause of their families being persecuted or being kicked out of the country by the regime.

“When I met Ramadan it was always at the forefront of his mind about how we were going to gain control of our country again. He was very passionate about the common cause and common good for Libya.”

He said the LIFG fought again Gaddafi in the mid-90s in the eastern side of Libya and was defeated in 1996. “It was a group that wanted to overthrow Gaddafi but they also possibly had some guys who were affiliated with al-Qaida. Did some of these guys carry the torch of al-Qaida? Possibly.”

In 2013, Ramadan resurfaced online and wrote a supportive post of another Libyan radical, Anas Al-Libi, who was given asylum in Manchester despite his involvement in a failed plot to assassinate Egypt’s then-president Hosni Mubarak. Libi was later captured in Tripoli by US special forces and charged with bombing US embassies in Kenya and Tanzania.

British support for Libyan dissidents changed abruptly after Tony Blair’s rapprochement with Gaddafi, sealed with the famous “meeting in the desert” in 2004.

Under Blair’s pro-Gaddafi policy, MI6 agents arranged the kidnapping of the LIFG leader, Abdul Hakim Bilhaj, and his deputy, Sami Saadi, from exile in Asia. Both were flown to Libya to be jailed and tortured, and they later successfully sued the British government.

During the 2011 Arab spring, British policy switched yet again, back to supporting Libyan dissidents, encouraging exiles, such as Ramadan, to return to Libya to fight Gaddafi, and contributing RAF warplanes to a Nato-led bombing campaign. Ramadan joined the revolution and afterwards settled in Tripoli.

In 2012, he posted a picture on social media of Hashem, then 15, holding a Kalashnikov with the caption: “Hashem the lion … training.”

In an interview in 2017, shortly before he and Hashem were seized by Tripoli militia, Ramadan proclaimed his innocence, saying: “We condemn these terrorist acts on civilians. We do not believe in killing innocent people.”