Clashes erupted on the edge of Cairo's Tahrir Square Thursday morning and continued into the afternoon as security forces attempted to drive protesters away from the nearby US embassy.

Protesters gathered at the embassy on Tuesday to condemn an anti-Islam film, The Innocence of Muslims, which gravely insults the Prophet Mohamed.

The protest turned violent on Wednesday evening and continued into early Thursday with exchanges of rocks, teargas and Molotov cocktails, along with chants of "The police are thugs."

By Thursday afternoon, most of the fighting was confined to the edge of Tahrir Square near the Omar Makram Mosque and Simon Bolivar Square.

Tahrir Square teemed with traffic as the fighting spilled over from the area around the embassy.

Despite the turbulence, two buses arrived on the other side of the square bringing foreign tourists to the Egyptian Museum.

Hundreds of security forces occupied Simon Bolivar Square adjacent to the US embassy, blocking off all the roads surrounding the area with police lines. Injured and unconscious officers were seen being carried by their colleagues away from the scene.

Security forces used teargas and shotguns loaded with bird shot to disperse the crowds and occasionally would charge at protesters in armoured vehicles, mounting the pavement at times. Few ambulances could be seen in the area.

Yassin Maher, 22, a day worker holding stones in his hands, told Ahram Online that he had just been released after serving an 18-month jail term and was protesting to demand better living conditions from Egyptian President Mohamed Morsi.

"As you can see, the security forces under Morsi are the same as those during the Mubarak era – both are defending America," Maher said.

"Of course, I'm also protesting against the insults to our Prophet Mohamed," added Maher.

Nasser Hassan, 30, a member of the Salafist Nour Party, said that he completely condemned both the violent protests and the heavy-handed response of the security forces.

"We delivered a message expressing our outrage [about the anti-Islam film] outside the embassy on Tuesday by chanting the name of the prophet, and that's enough," Hassan said.

"All Egyptians condemn this defamatory film and large groups of Christians have also announced that they would demonstrate on Friday in solidarity with the Muslims," he added.

Hassan went on to note that he had gone to the embassy on Thursday to urge his fellow Salafists to withdraw from the protest.

A Syrian man who was waiting to renew his visa at Tahrir Square's iconic Mugamma building, said, preferring anonymity: "This chaos is what the Americans want, but we trust President Morsi, who knows how to deal with them."

Additional reporting and video footage by Bel Trew