About 100 people staged the protest in Cairo on Sunday as part of the UN International Day in Support of Victims of Torture.
Protester Safa el-Mewelly said the police, who numbered several hundred, had struck him with batons. "They pressed in on us and they hit me in the leg," he said.
But the authorities did not break up the gathering, the latest in a series of street protests against the government.
Aljazeera's correspondent in Cairo Hussain Abd al-Ghani reported that the demonstration was the first time in recent years that Egyptian security forces had allowed anti-government demonstrators to gather outside the headquarters of state security.
The protesters included members of the banned Muslim Brotherhood, pro-reform activists and representatives of local human rights organisations.
The protesters demanded that
the interior minister resign
The demonstrators were protesting against the practice of torture to extract confessions from suspects, Abd al-Ghani said.
In the past 11 years, 300 cases of torture have been monitored by human rights organisations. Further, during the past decade, 120 prisoners have died in custody with evidence pointing to torture, he reported.
Many had been permanently disabled because of alleged torture. Several others had confessed to crimes they had not committed, Abd al-Ghani said.
Egypt's ruling National Democratic Party has denied the accusations. In the past five years, many cases have been referred to the attorney-general for investigation, the government said.
The protesters demanded the resignation of Interior Minister Habib el-Adli and an end to emergency laws, which opposition groups say are used against them.
"Freedom, freedom," chanted the protesters, who were allowed to walk through the centre of the capital. "Mubarak is null and void."
"State security, whose state security are you? You are state security of Egypt, not Israel," they shouted.
"State security, whose state security are you? You are state security of Egypt, not Israel"
Officials say accusations of torture by police are investigated and perpetrators prosecuted, but rights activists say the police generally turn a blind eye.
Mubarak, whose country has been a US regional ally, is widely expected to stand for a fifth six-year term in presidential elections later this year. But opposition groups have stepped up public criticism of him.
Washington has urged more political freedom in the world's most populous Arab nation. Recently, visiting US Secretary of State Condoleezza Rice criticised Egypt for emergency laws, arbitrary justice and violence against protesters.