"Do you [have sex with] her? How many times do you [have sex with] her a day?" the officer screams as he beats 23-year-old Ahmad Mahmoud, who was detained with a female colleague for participating in a demonstration in the Sudanese capital Khartoum.

Forcefully detained, verbally abused and tortured, Mahmoud, a rapper and university student, was arrested in Khartoum’s Bahary district on 2 February and held – along with several colleagues – for almost two weeks in a secret detention centre.

Mahmoud recalls how he was forced into a truck at gunpoint and taken to the detention centre, where he was threatened, interrogated and beaten on his back and shoulders with sticks and plastic pipes.

“I just disappeared. For several days my family had no clue what happened to me. I could have been dead as far as they knew,” Ahmad, a member of the Gerefna (“We’re Fed Up”) youth movement, told Ahram Online. “We were always being beaten. We could hear the screams of others being tortured, knowing that our turn, too, would come, and wondering how it was going to end.”

Mahmoud was only one of at least 100 people arrested by the authorities in Khartoum and second city Omdurman in late January/early February of last year, according to Human Rights Watch. The arrests followed a wave of demonstrations in the capital calling for regime change.

Mahmoud’s story is one of many nightmarish accounts of how torture has been systematically employed inside Sudanese prisons – known as “ghost houses” – over the last two decades. The facilities are used by authorities to detain political adversaries, many of whom would simply “disappear” for months.

“Torture and police brutality have become one of the most effective tools used by the government to maintain the regime in the face of growing public dissent,” said rights lawyer Salih Mahmoud Osman. “Anyone speaking out against the government could be picked up off the street. Students and young people appear to be the most common targets.”

The most recent example to be documented by citizen journalists is the case of 29-year-old engineer Mohamed Hassan Alim, seized by Sudan’s National Intelligence and Security Service (NISS) on 26 December following the appearance online of a video in which he is seen criticising presidential advisor Nafi Ali Nafi. In the video, Alim, during a recent symposium at Khartoum University, openly accuses Nafi – along with the entire regime of Sudanese President Omar Al-Bashir – of corruption, nepotism and flagrant human rights infractions.

During his detention, activists launched an awareness campaign on social-networking sites (#FreeAlim on Twitter). The video in which he confronts Nafi has racked up over 243,000 views on YouTube and was circulated widely on Facebook and Twitter. Several Facebook pages have also sprung up to express solidarity with the detained activist.

Alim, dubbed “Sudan’s Bouazizi,” in reference to the Tunisian street vendor whose self-immolation in late 2010 triggered the so-called “Arab Spring,” was released yesterday after spending 24 days in solitary confinement. Alim was initially arrested from his home by armed men in plainclothes in Khartoum’s Haj Youssef district while his stunned neighbours looked on. He was then taken to the notorious Kober Prison, the country’s main detention facility for political prisoners.

“I went to visit friends, then came back to find my son had been taken,” Alim’s mother, Kawthar Mohamed Omar, recalled. “I knew something was going to happen to him after that video came out. But my son is headstrong and courageous – no one could stop him from speaking out.”

It was hardly Alim’s first brush with the law. He was detained several times by security agencies since becoming politically active in 2003. The last time was in January of last year, when he was held for a total of 45 days. “During this period, I didn’t see my son once,” said his mother. “I didn’t even know if he was alive.”

Alim is one of at least 73 students to have been detained in the capital within the last 30 days. The wave of arrests coincides with the first anniversary of the call for revolution in Sudan on 30 January of last year, after which Alim and dozens of colleagues were arrested.

Since mid-December 2011, security forces have used excessive force to break up student demonstrations at universities across the country, Human Rights Watch stated on 3 January. On 22 December, police and internal security forces – wielding batons and firing teargas – dispersed a peaceful student protest at Khartoum University held to express solidarity with a local community recently displaced by construction of a dam on the Nile River. Numerous student protesters were arrested without charge.

Reliable figures for the number of political detainees currently held by the NISS or at prisons throughout the country are unavailable.

“Many victims are traumatised after being subject to lengthy detention or under continuous threat for so long, sometimes months,” said rights lawyer Saleh Mahmoud Osman. “So they aren’t willing to raise the issue with lawyers or the media out of fear of further detention or even death – so many go undocumented.”

Osman, who hails from Sudan’s troubled Darfur region and was himself arrested and tortured on more than one occasion for his political activity, worked at the Nyala-based Al-Amal Centre for the Rehabilitation of Victims of Violence from 2004 to 2005. He says that many of the victims that had visited the centre, especially women who had been sexually assaulted by security personnel, had refused to file legal cases against the government out of fear of reprisal.

Over the course of an entire year, the centre was only able to bring one out of hundreds of cases to court. Members of the Janjaweed militia, which is allegedly backed by the government, attacked a vehicle carrying a minor and violently raped her. “They were only convicted by the court because they admitted to committing the crime,” said Osman. “And they were eventually released.

“Perpetrators are very rarely brought to justice by the Sudanese judicial system mainly because they’re given impunity and are thus beyond the reach of the law,” he added.

The National Security Act, passed by Sudan’s national assembly in late 2009, contains several articles that are in clear violation of Sudan's 2005 interim constitution, says Osman, who was part of the opposition bloc in parliament that voted against the bill. The legislation, the lawyer points out, “grants security officers unrestricted powers to search, arrest and detain people without charge or trial.”

“The NISS has systematically used torture to extract information or to break the dignity of detainees,” the African Centre for Justice and Peace Studies (ACJPS) – which is based in Africa, London and New York – declared in a recent report. The report goes on to identify several commonly-cited rights violations associated with pre-trial detention, including torture and death in custody, lack of access to medical treatment and sub-standard prison conditions.

In March 2008, two people were tortured to death in Khartoum’s Al-Faiha police station while in custody. The first victim, Mohamed Al-Jaili, died as a result of repeated blows to the head by a blunt instrument. The second, Babikir Sulaiman, died as a result of respiratory and blood-circulation failure, while evidence of severe beating was found on several parts of his body, the ACJPS noted. In mid-2010, a court acquitted the ten policemen accused of killing the two men.

Wagdy Saleh, 44, currently serving on Alim’s 30-member defence team, was himself arrested and tortured several times, most recently in 2003 when he was held by authorities for five months.

“I was thrown into a cell reeking of urine, where I would be severely beaten,” Saleh recalled. “I was ordered to lie down on my back while the guards would kick me. Sometimes I would be forced to stand up for two days at a time while they doused me with freezing water.”

But according to Osman, “novel modes of media, along with ongoing revolutions all over the Arab world, have empowered young people, allowing them to bring pressure to bear on the government.” Sudan’s young activists, he added, “are now breaking the wall of fear and silence.”

Early last year, 24-year-old female Sudanese activist Grififna Safiya Eshaq appeared in a YouTube video in which she recalled how she, along with several colleagues, had been gang-raped by plainclothes security agents after having taken part in an anti-government protest.

“After our release, we decided that – if we really want change – we have to speak out and tell everyone about our detention and the torture we faced,” said Mahmoud.