Clashes between police forces and protesters, which have erupted intermittently since Monday afternoon, continued into Tuesday evening after protesters regrouped on Qasr Al-Eini Street adjacent to Tahrir Square.
Protesters of unknown affiliations attempted to break into the Shura Council building and the nearby Qasr Al-Eini Hospital, according to state-run news agency MENA. The entrance to the square from Qasr Al-Eini Street has also been closed off.
Gunfire was still being heard intermittently around the flashpoint square, according to MENA. Earlier Tuesday evening, an Ahram Online reporter saw volunteer doctors attempting to remove birdshot pellets from a protester's body.
Skirmishes broke out Monday afternoon when protesters commemorating the anniversary of last year's Mohamed Mahmoud Street clashes began fighting with Central Security Forces near interior ministry headquarters on Nubar Street.
It remains unclear, however, why the clashes erupted. The interior ministry, which admitted using teargas against protesters, said that fighting began when "lurkers" threw stones and Molotov cocktails at security officers on Qasr Al-Eini Street.
Dozens were injured in the subsequent clashes, including two currently in critical condition.
Eight policemen and 20 soldiers were injured during the clashes on Monday, the interior ministry said.
Human rights activists and lawyers said a number of protesters had been arrested in Tahrir Square early Tuesday morning.