Egyptian security forces and protesters clashed for a second successive day in central Cairo today in scenes not seen since the uprising that toppled Hosni Mubarak in February.

Riot police were deployed around the interior ministry and used tear gas to keep the protesters at bay. The demonstrators were responding with rocks and firebombs.

The clashes left streets littered with rocks and debris and sent a cloud of tear gas over the area.

Today's violence comes after 5,000 protesters battled police for hours overnight.

Dozens of protesters and policemen were injured in the clashes, but there were no exact figures immediately available. Ambulances were ferrying the wounded to hospitals and volunteer doctors and nurses were treating others on pavements.

Many of the protesters are believed to be relatives of 850 people killed during the uprising that ousted the former president, and are frustrated over what they perceive as the slow pace of prosecution of police officers believed to be responsible for the deaths.

The clashes began at Tahrir Square, epicentre of the January 25 to February 11 uprising, but later moved to streets leading to the nearby interior ministry when authorities ordered riot police to pull back from the vast plaza. Tahrir Square was closed to traffic today.

The military, which has taken over from Mubarak, issued a statement on Facebook saying the clashes were designed to "destabilise the country" and drive a wedge between the groups behind the uprising and the security forces. It called on Egyptians not to join the protests.

A key youth group, April 6, described the police's handling of the protests as "brutal" and called for a sit-in in central Cairo to protest against what it said was the failure to implement many of the revolution's demands and also to show solidarity with the families of the uprising's victims.