"Volunteers must be aged 18 or over" reads a fresh banner flying over the gate to the military training base in Benghazi, seat of the Libyan insurgency against strongman Moamer Kadhafi.
Inside the revamped former Libyan army base, on a vast sun-scorched parade ground, several hundred would-be soldiers alternate between star-jumps and bursts of laughter.
A sun-burnt drill instructor, whose beard has already turned white, tries to teach the rookies how to stand to attention.
Due to a shortage of uniforms, most of the trainees are still in the jeans and T-shirts with which they arrived at the "February 17" camp named after the launch of the revolt that has turned into a military deadlock.
"There are about 600 of them now," says Imed el-Obaidi, a 21-year-old electrical engineer who returned from the United Arab Emirates at the start of the uprising.
"They come in the morning, break for breakfast, and carry on until lunchtime," explains Obaidi, who joined the rebels' special forces but is filling in as a media officer while a hand injury keeps him out of action.
Mohammed Faraj, a wrinkled, white-haired former captain in Kadhafi's army, is one of the instructors. At 61, he retired 11 years ago but when the revolt broke out he dusted off his combat gear, which he now wears with black mocassins.
"I mobilised straight away. I knew that the kids fighting had no idea how to handle weapons, so I'm teaching them how to use rocket-propelled grenades and American missiles."
Out of the blue, a soldier fires off three shots from his automatic rifle. The recruits jump with fear, which quickly turns to laughter.
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"Some will join the army and go to the front. Others will quit during training, which takes a month to complete. They are free to choose," Obaidi explains.
He personally wants to return to the front but will not stay on in the army. "I have a Master's degree," he says, "and I must finish my PhD -- as I promised my father I would."
One third of the recruits were living overseas when the revolt started in mid-February, Obaidi says.
"I want to fight for Libya, to defend my country, my heart," says Walid Zemit, a student who returned from Coventry in England two weeks ago and now lives at the military base.
At his side is a silent, serious-looking older man wearing a woollen hood despite the midday heat.
Ahmed Zidane, 47, hails from Brega, the frontline town 240 kilometres (150 miles) west of Benghazi. He stands alongside rookies young enough to be his children.
"I was a petroleum engineer, working for Sirte Oil Company," he says. "There was too much corruption under Kadhafi. We have to stop him. It's a duty, a battle between good and evil."
The better-trained trainees have advanced to urban combat exercises and house-to-house fighting. They carry automatic weapons but are still firing blanks so as to avoid accidents.
"Attacking a house takes organisation: some men in front, others at the back. Everyone has their position. It's a bit like a football match," according to Obaidi.
In another group, a recruit wears a white woollen hood, apparently because he comes from Tripoli and does not want to be recognised.
Nuri Mohammed, a 20-year veteran of Kadhafi's army in which served as a captain, is now an urban combat instructor at the camp and proud of the recruits under his wing.
"They learn fast. Half of them are engineers, intellectuals," he says.