(CNN) -- Egyptian doctor Amany Sadek was treating patients in a makeshift hospital close to Cairo's Tahrir Square on Monday when the building was surrounded by armed forces.
The doctors turned their lights off, kept quiet and were unable to let anyone in or out of their doors.
"It was horrible, we could hear shots outside," said Sadek.
"We carried on treating patients in the dark. When we opened the doors an hour or so later, we found people desperately looking for somewhere to be treated.
"I was scared and my friends were scared, but you kind of get used to it," she said. "Despite the attacks, the hospital is still one of the safest places to be."
Sadek is one of the founders of the Tahrir Doctors Society, a group of volunteers that formed after spontaneously treating protesters injured during Egypt's revolution in January.
Last Friday, when violence broke out between protesters and security forces after the second round of voting in parliamentary elections, the society set up its makeshift hospital for the fifth time this year.
The interior ministry has said at least 100 security officers have been wounded in the clashes. CNN has not been able to independently verify this claim.
The field hospital in Omar Makram mosque near Tahrir Square was still in place and stocked with necessary supplies since the last clashes in November. The doctors were able to re-open it quickly to treat victims of the new wave of violence.
"We got a call at 5 a.m. to say the army were attacking people sleeping in their tents," Sadek said. "By the time we got there we found lots of casualties, so we re-opened the hospital and it was ready to go straight away."
"We have treated over 1,000 wounded patients since Friday, and lots of people have been transferred to other hospitals for surgery.
"We are seeing all kinds of injuries, many from live bullets."
The society said on Saturday that one of its members had been shot in the stomach and others had been threatened with arrest.
Tahrir Doctors Society currently has about 20 volunteer doctors on duty at any time of the day or night. It's facility is a short distance from Tahrir Square; other makeshift hospitals closer to the scene of the clashes have had more trouble continuing with their work.
"The army attacked one of the other field hospitals. The doctors were told to leave or they would be attacked, and the army took their drugs and burned them," Sadek said.
"Others have been surrounded to prevent anyone from entering or leaving. That happens on a daily basis, usually late at night."
Maj. Mohamed Askar of THE Supreme Council of the Armed Forces said protesters were capturing and wounding soldiers.
"The army soldiers they kidnapped and returned are now in the hospitals. The rebels also captured three officers, tortured them and released them. They were even talking about a prisoner swap," he said.
Sadek says the violence of the last few days is the worst she has seen. At least 14 people have been confirmed killed in the latest spate of violence.
Sadek said: "This time it's more brutal than ever, more even than in January and February."
Tahrir Doctors Society was formed by a group of five doctors who met in January during the protests that led to the resignation of President Hosni Mubarak 18 days later.
"The five of us sitting in a cafe during the revolution. We were talking about the need to change things, and we started the Tahrir Doctors Society," said 29-year-old facial surgeon Amhad Farouk.
The aims of the society are to provide emergency intervention during clashes or disasters, and to campaign for the right of healthcare for every citizen.
Dr Farouk said: "We do not discriminate between any groups in treating them: we will treat security as well as protesters. We are part of the revolution, and it is the revolutionary spirit to treat everyone equally."
He added: "At first we weren't organized enough to keep records, but in the recent clashes we keep records of what happens to each patient. We treated more than 3,000 people in one week."
Volunteers coordinated thousands of public donations of medical devices and drugs through accounts such as @TahrirSupplies and @TahrirNeeds on the micro-blogging site Twitter.
"We would announce through them what we needed and people contributed millions of pounds worth of supplies," Dr. Sadek said.
"Normal people would buy what we needed from pharmacies or factories and bring it down to the square. It was very inspiring."
The group was able to draw on training its members had received from the international medical charity Medicins Sans Frontieres.
"We learned that the safest place for our bigger makeshift hospital was back from the front line, so patients with major injuries could be transferred there from the front line," Sadek said.
"Many doctors in the front line units were injured by the gas. It went on for six days. Whenever I ha
d to go to the front line, I wore a gas mask and goggles and still could hardly breathe."
During quieter times, the Tahrir Doctors Society continues its humanitarian work providing free traveling clinics in deprived areas.
A mission that Dr. Farouk said was inspired by January's revolution.
"This is the rise of Egyptian society. All sorts of groups are organizing themselves since the revolution and are getting stronger," he said. "The idea of volunteering is really taking off."
Dr. Sadek agreed.
"Before the revolution people never thought about volunteering. Doctors were just trying to earn enough to make a living, not participating or sharing," she said.
"After the revolution people started to believe in themselves again. Now we have realized we can make a difference and have stopped thinking just on a personal level. It's so satisfying."