Hundreds of protesters rallied on Friday in Cairo against President Mohamed Morsi, a much smaller turnout than hoped for by activists bent on challenging the country's first Islamist president.
In Cairo's Tahrir Square, where hundreds of thousands rallied to overthrow president Hosni Mubarak early last year, several dozen of Morsi's opponents briefly clashed with his supporters before withdrawing, witnesses said.
"Morsi has men backing him," his victorious partisans chanted. Four people were injured in the clash, including three with birdshot wounds, the official MENA news agency quoted a medic as saying.
In northern Cairo, hundreds of people gathered near the presidency, which Morsi has occupied since his inauguration in June, chanting "down with the Supreme Guide's rule."
They were referring to the leader of the influential Muslim Brotherhood, to which Morsi belongs.
Police were deployed to ensure the protests remained peaceful, a security official told MENA.
The protests take place as Morsi, who assumed office amid a power struggle with the once-ruling military, consolidates his authority and as two journalists critical of the president stand trial.
The protest organisers demanded that Morsi repeal an interim constitution in which he took over the military's powers to legislate in the absence of parliament, which the army dissolved shortly before his election.
He also sacked military chief Field Marshal Hussein Tantawi and other senior army officials who had ruled the country since Mubarak's overthrow.
Brotherhood officials said they believed that the anti-Morsi protesters had hoped that the military would intervene against Morsi if mass protests broke out, repeating the scenario that forced Mubarak to resign.
The protest organisers appear to be a mix of ardent secularists and activists nostalgic for Mubarak's rule, such as television station owner and show host Tawfiq Okasha, who faces trial next month.
Okasha, whose station has been banned from broadcasting, faces charges of trying to incite Morsi's murder.
The trial of another journalist, Al-Dustour newspaper editor Islam Afifi, began on Thursday.
Afifi was briefly detained after the hearing before Morsi, using his contested legislative authority, amended the law allowing detention pending a verdict for media crimes.