Egyptian opposition groups clashed with security forces after rights groups accused undercover officers of beating to death an activist who had attempted to expose police corruption.

Police have denied any role in the death of Khaled Mohammed Said, 28, who the Interior Ministry said on Saturday died from an overdose of drugs he swallowed before police approached him.

Some 200 protestors chanting anti-government slogans, were quickly surrounded in Lazougli Square near the Interior Ministry in downtown Cairo, a Reuters witness said.

'Khaled was murdered and Adly is responsible,' protestors chanted, calling for Egyptian Interior Minister Habib el-Adly to be held accountable for Said's death.

The violence began when demonstrators tried to break through a police cordon. A security official said 32 protestors were detained.

'We are here protesting the loss of the martyr of the emergency law,' said Ahmad Raghab, head of the Hisham Mubarak Law Center, referring to an Egyptian law that allows indefinite detention and curbs anti-government political activity.

'We demand that those responsible for his death are tried.'

Egypt last month extended until 2011 an emergency law that gives police wide-ranging powers including indefinite detentions without charge and limiting the freedom of public assembly to no more than five people.

The measure has been extended regularly since it was passed in 1981, but authorities say they have now limited its scope to terrorism and drug cases. Activists and analysts say the law is used to crush dissent.

According to activists and human rights groups, Said was killed in the port city of Alexandria on June 6 after he posted an internet video which Said's family said showed police officers sharing the profits of a drug deal.

The El-Nadeem Centre, a rights group following the case, said undercover policemen confronted Said in an internet cafe, dragged him onto the street and beat him to death. Social networking sites posted images of his beaten face and body.

Egypt's attorney general has ordered an autopsy and referred the investigation into Said's death to Alexandria's appeals court. Rights group Amnesty International has called for an independent investigation into Said's death. – Reuters