Nearly a dozen policemen stripped a protester, aged between 40 and 45, and beat him up outside the presidential palace in Cairo as the unrest against Mohammed Mursi intensified.

The police personnel used brute force on the man as he tried to escape. While some dragged him, others held his hands and legs. They then rained blows on him and kicked him. The helmeted riot police, who were deployed outside the palace, continued beating the man, ignoring his pleas for mercy.

Images aired by Egypt's al-Hayat channel show security personnel later pushing the man into a police van.

While the police high-handedness has evoked widespread shock, officials have offered to launch an investigation into the incident.

Many opposition groups including the main anti-Mursi bloc National Salvation Front have urged their activists to withdraw from their rallies as the demonstrations are becoming increasingly violent.

The stripping incident allegedly took place in the evening following the Friday protests which saw one protester killed during clashes. The demonstrator was reportedly shot dead.

Dozens of others have also been injured in the clashes between police forces and the demonstrators. Most of them were injured in clashes outside the presidential palace.

"I am here because I want my rights, the ones the revolution called for and which were never achieved," a protester outside the palace, named Mohamed Ahmed, told Reuters.

While the protesters hurled petrol bombs, the police personnel responded by firing water cannons and teargas in a bid to bring the situation under control.

Scores of protesters took to the streets in Cairo and across Egypt demanding the ouster of Mursi.

"We brought down the Mubarak regime with a peaceful revolution and are determined to realise the same goals in the same way, regardless of the sacrifices or the barbaric oppression," wrote the liberal politician Mohamed ElBaradei in his Twitter account.