Egypt's army has violently retaken Cairo's Tahrir Square from protesters, less than 48 hours before the former president Hosni Mubarak is to stand trial in the capital.

Armed riot police and soldiers fired into the air as tanks moved in on Tahrir, which has been occupied by demonstrators for more than three weeks. Witnesses said some protesters were taken away.

Activists accuse Egypt's ruling military generals of dragging their feet on any meaningful reform in the country and warned that the revolution that toppled Mubarak earlier this year was in danger of being hijacked by conservative forces.

Eyewitnesses reported swarms of security personnel storming the square from several directions, smashing tents and stalls before dragging away some protesters into military detention. Egypt's cabinet office said "thugs" had been arrested.

Some locals cheered as the sit-in was dispersed, highlighting a growing division over tactics at the heart of the protest movement. Around 30 of the political forces participating in the occupation had decided to suspend their involvement throughout the Muslim holy month of Ramadan, which began on Monday. But several hundred hardcore demonstrators remained in Tahrir, including some relatives of those killed in the anti-government uprising this year, vowing only to leave when Mubarak had faced justice.

"When normal people beat us in Abbasiya, that was painful," wrote one activist on Twitter, referring to clashes last week which left dozens injured. "To hear that people are cheering [today] because the army beat martyrs' families, that's devastating."

Local news outlet al-Shorouk said military personnel went on to destroy a series of recently installed revolutionary artworks inside Sadat metro station, which lies underneath the square. The move is likely to further exacerbate tensions between revolutionaries and the supreme council of the armed forces (SCAF), which has been forced to defend itself in recent weeks against claims that it is not truly committed to democratic transition or the holding of former regime officials to account.

On Sunday night the army's chief of staff, Sami Anan, denied suggestions that SCAF had cut a deal with the Muslim Brotherhood, guaranteeing the country's largest Islamist group a strong showing in November's parliamentary elections in exchange for the organisation providing political support to the military. Anan accused some media outlets of fuelling sedition and insisted the military was seeking to return to barracks as soon as possible.

He also responded angrily to repeated allegations from protesters and human rights groups that some pro-change demonstrators were being held in military detention and tortured, calling on those making the claims to furnish proof. Several local and international campaign organisations have published details of arbitrary arrests and subsequent military abuses since the fall of Mubarak more than six months ago.

The latest unrest comes as the nation gears up for the beginning of Mubarak's trial, which is due to open on Wednesday. At the weekend the attorney general, Abdel Meguid Mahmoud, issued a formal summons ordering the toppled dictator to be transferred to Cairo from his current location, a hospital bed in the Red Sea resort town of Sharm El-Sheikh, where the 83-year-old has been under detention since April.

Mubarak will answer a series of charges relating to economic fraud and the unlawful killing of protesters, and will stand in the dock alongside his two sons, his former interior minister, Habib El-Adly, and a number of other senior regime officials. The court case will be heard in a tightly secured police academy on the outskirts of the capital, and broadcast live on state television.