Egyptian youths threw petrol bombs and fired guns in clashes on Tuesday near Cairo's Tahrir Square, where protesters have been camped out demanding the military hand over power to civilian rule, witnesses said.
An organiser of the sit-in protest said the trouble started when an unidentified group had tried to enter the square. State media said the clashes were between protesters and street vendors but this could not be independently verified.
At least 10 shots were heard as the trouble flared near the Egyptian museum at one end of the square, where protesters have been urging the departure of the army generals who replaced Hosni Mubarak in February.
Two protesters suffered eye injuries in the violence, the state news agency MENA reported. An ambulance was seen driving into the area.
The violence disrupted what had been two largely peaceful days of voting in the first phase of a parliamentary election, the first since Mubarak was ousted.
The square, where the protesters have been camped out since November 18, has been calm for several days. Last week, roads around Tahrir were the theatre for some of the worst violence since Mubarak was toppled: 42 people killed in Cairo and elsewhere in violence triggered by protests against the generals.
The protesters say the generals are trying to manipulate their position to preserve power and privilege. The generals say they will hand power to an elected president by mid-2012.
The television footage showed petrol bombs arching through the night sky and exploding on the road by the Egyptian museum and close to the protesters' encampment.
Mohammed al-Saeed, speaking to Egyptian state television, said the protesters had organised volunteer security groups to protect people and families in the square from the youths.
It was unclear who threw the petrol bombs and who fired the shots and what motivated them, but state television said earlier clashes had involved street vendors.
In an earlier sign of tensions in the square, scuffles had flared between dozens of street vendors who have been selling goods to the protesters camped out there.
The flare-up prompted medics working in the square to step in to stop the scuffles, they said. Some of those involved in the brawl wielded sticks and vendors' stalls were damaged.
(Additional reporting by Reuters Television, Dina Zayed, Ali Abdelatti and Peter Millership; Writing by Edmund Blair and Tom Perry; Editing by Andrew Roche)