Egyptian officials have tortured a 24-year-old prisoner to death, provoking accusations that the increasingly unpopular junta is failing to dismantle Hosni Mubarak's brutal security apparatus.

Essam Ali Atta, a civilian serving a two-year jail term in Cairo's high-security Tora prison following his conviction in a military tribunal earlier this year for an apparently "common crime", was reportedly attacked by prison guards after trying to smuggle a mobile phone sim card into his cell.

According to statements from other prisoners who witnessed the assault, Atta had large water hoses repeatedly forced into his mouth and anus on more than one occasion, causing severe internal bleeding. An officer then transferred Atta to a central Cairo hospital, but he died within an hour.

The death occurred less than 24 hours after two police officers in Alexandria were each sentenced to seven years in jail for their part in the murder of Khaled Said, a young businessman beaten to death by security forces in broad daylight last year. That incident led to the creation of the Facebook group "We are all Khaled Said" and helped mobilise a wave of protests which eventually toppled Mubarak in February.

On Friday, a new Facebook page entitled We are all Essam Atta appeared online, and quickly attracted thousands of supporters. Activists and human rights campaigners flocked to social media sites to express their fury at Egypt's ruling generals, whom many now view as indistinguishable from the Mubarak regime they replaced.

"Nothing, absolutely nothing, has changed," Aida Seif el-Dawla, co-founder of the El Nadeem centre for the rehabilitation of victims of torture, told the Guardian. "There is nothing rogue about this killing, and nor was it about the mentality of the security officers. It was about official policy and the systematic use of torture in our security system. Those who tortured Essam to death could not have done so unless they knew they were going to get away with it."

Calls are now growing for Egypt's public prosecutor to order a full autopsy on Atta. Sources close to Atta's family say they are resisting pressure from the authorities to carry out a quick burial.

Atta's death is the latest in a long line of official torture incidents that have hit the headlines since the Supreme Council of the Armed Forces (Scaf) took power almost 10 months ago. In March, a number of female protesters claimed they were subjected to forced "virginity checks" by soldiers after being detained at a reformist demonstration, and in subsequent months several deaths and assaults of Egyptians at the hands of police officials have been reported.

In September, a video emerged (warning: disturbing content) of unarmed detainees in Daqhaliya governorate being repeatedly slapped, hit and electrocuted by police officers while in custody. Then, on 9 October, Scaf was accused of direct involvement in the worst night of violence seen in Egypt since the anti-Mubarak uprising, with at least 27 people left dead after armoured personnel carriers mowed down groups of protesters.

"Scaf is not a department within the state, it is an extension of Mubarak – nothing less," claimed Dawla. "They have sacrificed Mubarak, but exactly the same regime is still in place, displaying the same language, the same attitude, the same contempt for the Egyptian people."

Egypt is gearing up for parliamentary elections, which will be held in several phases beginning on 28 November. However, under Scaf's current "transition timetable", the military generals will remain in executive power until well into 2013. A number of political parties have already said they will boycott the poll.