German engineer Wilfried Siewe is now a free man after being held in a Cameroon prison for nearly two years. 

"I am very very happy to see the family again," said Siewe, referring to his wife and two children at a virtual press conference held on Thursday. "It was a tough time during which I really couldn't tell when it was going to end or how."

"I just need some time to sort myself out and live a normal life again."

Siewe, who was born in Cameroon, was released from Yaounde Central Prison on Saturday and returned to his home in southern Germany earlier this week.

Detained for allegedly trying to destabilize Cameroon

He was arrested in Cameroon in January 2019 on the last day of a family vacation after police saw him snapping photos of a justice building in the capital, Yaounde. 

When officers searched his mobile phone, they found a WhatsApp video of a protest against the government of President Paul Biya that was held in Germany's capital Berlin. Some sources report that Siewe also had books in his possession by Cameroon opposition figures. 

Siewe was detained on suspicion of being a threat to state security. Although he was later able to prove that he was neither in Berlin nor attended the demonstration, he was still held by authorities. He was later sentenced for alleged participation in a 2019 prison riot.

In an interview with the German TAZ newspaper in November, his wife Layoko Siewe said she believes her husband was detained "to set an example" to the diaspora, who often speak out against Biya.

After Biya won presidential elections in 2018 for a seventh consecutive time, Cameroonians living in Europe protested his victory in Paris, Brussels and Berlin. 

Biya tightens screws on opposition dissent

Biya's regime has long been criticized by human rights organizations for using arbitrary detention to lock up opposition voices. 

"People simply exercising their right to freedom of peaceful assembly and demonstration have paid a high price with prison terms based on trumped-up charges," said Fabien Offner, Amnesty International West and Central Africa researcher, in a press statement on Thursday that referred to further detentions of protesters in September.

"The authorities must immediately put an end to the mass arbitrary arrests and detentions and immediately release prisoners of conscience."

Read more: 'No dictatorship considers protests legal,' Cameroon's opposition politician says

Maximilienne Ngo Mbe, the Executive Director of the Central Africa Human Rights Defenders Network, said the rights situation in Cameroon was getting "worse by the day." 

"Instead of making progress, the country is regressing," Mbe told DW from Douala, Cameroon's largest city. "In Central Africa, Cameroon tops the list when it comes to rights violations and arbitrary detention: arrests of activists and rights defenders are rife."

Arbitrary arrests especially common in the Anglophone regions

Activists, politicians and academics from Cameroon's Anglophone regions in particular continue to languish in Cameroon's prisons.

One of these is is 36-year-old radio presenter Mancho Bibixy, who is imprisoned in the same jail where Siewe was held. 

Bibixy was initially sentenced to 15 years for alleged rebellion, spreading false information, and for taking part in protests in the Anglophone regions, among other charges.

His arrest was deemed "arbitrary" by the UN Group on Arbitrary Detention. 

"Life has been difficult for me, just like any other prisoner," Bibixy told DW in a telephone interview from jail. "Especially because I'm in prison far away from my family."

"The second thing is the prison conditions, overcrowding, the system, water shortage, electricity, illnesses. All of that makes life very difficult in prison."

According to the World Organization against Torture, Bibixy shares a prison cell with 15 other inmates. His health has deteriorated, reports suggest. 

Bibixy says his main crime was marching and protesting against the Biya government, which isn't illegal under Cameroon's laws. "I don't know why they went ahead to sentence me."

Bibixy's protest launched the 'coffin revolution'

In November 2016, Bibixy took a loudspeaker and a coffin to a crowded roundabout in Bamenda, the capital of the English-speaking North West Region. Standing inside the open casket, he spoke out against the social and economic marginalization of the Anglophone regions. 

At that time, the regions were seeing growing grievances following a new requirement for all schools and courts to use the French language instead of English.

Bibixy's action would later come to be known as the "coffin revolution."

What initially started as anti-government protests have since bloomed into a deadly conflict between Anglophone separatist fighters and government troops. 

The violence has claimed more than 3,000 lives and displaced more than 600,000 people. In its World Report 2020, Human Rights Watch accuses both sides of committing atrocities. 

Read more: Rights groups call for cease-fire in Cameroon

On top of his original sentence, Bibixy has been given an extra 18-month sentence for his alleged role in the 2019 prison mutiny. 

The cases of Mancho Bibixy and Wilfried Siewe are "a travesty of justice", according to rights defender Maximilienne Ngo Mbe. 

"Mancho in particular is an example of gross human rights violation in Cameroon, of how innocent people are arbitrarily arrested and detained by a group of selfish individuals," she said. 

"While they are in jail, they don't have access to their lawyers and family. They are also being tried in military courts which is unacceptable and violates African Union conventions."

Read more: Cameroon army confirms TV anchor's death in detention

Following his trial, Bibixy said he lost faith in the country's legal system.

"I don't believe in the judicial process in Cameroon. I think that they are not independent," Bibixy said. "All the witnesses who came, none of them identified me as having any problem, or they didn't prove that I was guilty of any of the charges."

"I continue to think that I was illegally arrested and illegally detained," Bibixy said.

Mimi Mefo Takambou contributed to this article.