While protesters gathered outside the building of the doctors' union, known as the Egyptian Medical Syndicate, inside members called for the resignation of the health minister — in part because of his lack of support — and threatened to go on partial strike.

The standoff between policemen and doctors suggested that Egypt's powerful security forces may have overstepped their limits by clashing with one of the country's most respected professions. On Friday, the Arabic hashtag "support the doctors' syndicate" was trending on Twitter in Egypt. The Egyptian Initiative for Personal Rights, a prominent local rights group, said the doctors' assault was "a reflection of the level of police abuse of authority these days."

The protests were sparked by an assault on Jan. 28 in Cairo's Matariya hospital, one of the largest in the city, which serves around 2,000 patients a day drawn from one of Cairo's poorest neighborhoods.

The hospital entrance is surrounded by piles of garbage, and the surrounding streets are crowded with hawkers selling everything from used clothes to chickens freshly slaughtered on the pavement. A police office is attached to the hospital building so that officers are on hand to intervene in the regular scuffles.

Around 10 minutes' walk away is Matariya's main police station, described by the initiative for personal rights as a "slaughterhouse" because 14 people have died while in police custody there over the past two years.

The deputy head of the hospital, Mamoun Hassan el-Deeb, told The Associated Press that two young doctors named Ahmed Abdullah and Moamen Abdel-Azzem were attacked by two policemen — the officer with a scratch on his forehead and his colleague.

According to the online and televised testimonies of Abdullah and Abdel-Azzem, they were beaten up by the policemen and one officer pulled out his gun and threatened other hospital staff.

A vehicle carrying around seven more policemen then rushed from the station to arrest the doctors, according to a nurse who witnessed the assault. When one of the doctors tried to resist, he fell to the ground and a policeman stomped on his head with his boots. She spoke on condition of anonymity because of fear of reprisal. The nurse was among a dozen hospital staffers who later testified in front of a prosecutor.

Inside the police station, high-ranking policemen intervened to rescue the doctors and offered an apology.

"The apology was not accepted by the doctors, who were deeply humiliated," hospital chief el-Deeb said.