The crowd hurled projectiles and insults at the soldiers sent to defend the ministry after 11 people were killed in clashes on Wednesday, and called for the overthrow of the head of the army council, Field Marshal Hussein Tantawi.
The army fired water cannon then teargas, and riot police surged towards the crowd with batons. Scores of wounded protesters were taken away on motorcycles and dozens of soldiers were injured.
“O Tantawi, good morning, this is your last day,” shouted the crowd.
The violence came three weeks before an election that is the first chance for Egyptians to freely choose their leader. A successful vote would mark the most important step in a messy transition to democracy since the overthrow of Hosni Mubarak 15 months ago.
The troops pressed forward when protesters began cutting through barbed wire used to seal off the ministry building in Cairo’s central Abbasiya district.
Protesters ripped down a metal fence at an underground railway construction site to build a barricade.
The teargas scattered the crowd down rock-strewn streets, where they regrouped. Troops blocked off a street to the ministry using armoured personnel carriers and fired shots in the air.
“The crowd is coming here with sharp weapons. We have batons and water cannon and teargas to disperse them,” said one commander. “Some of them believe if they kill a soldier they will go to heaven. What do you expect us to do?”