I'm only 16. They gave me a rifle. It was heavy.

They said we had to go forward. If we came back, they would shoot us.

Darchiga Kuken was sheltering in a bunker in the Mullaitivu area when a group of about 20 Tamil Tiger soldiers arrived and demanded that she went with them.

"I was sick with chicken pox. My mother and father were screaming and crying, saying that I was sick and pleading with them not to take me," she said. The men went away. And then at 5pm on 14 March they came back. They called me to come out and then they grabbed me and put me in a jeep. I started to cry. I was shouting: 'Mother, father, help me.' "

The 16-year-old is now being held in what the government describes as a "rehabilitation centre", a jungle camp built on a hillside outside the town of Ambepusse in the south of the country. Here children like her, who were forced to fight on the front line in the final stages of the war in Sri Lanka, gave the Observer compelling evidence of war crimes committed by the Liberation Tigers of Tamil Eelam (LTTE).

The camp currently houses 95 children, with another 200 on their way from internment camps around the town of Vavuniya in the north of the country.

Despite international concerns over the treatment of LTTE suspects, the children appeared to be well treated and were able to speak freely when the Observer visited the camp on Thursday. The most distressing sight was a young boy howling in pain on the floor of one of the huts; his friends said that he had recently arrived and still had a piece of shrapnel lodged in his skull from the recent fighting.

The accounts of these boys and girls who surrendered to the Sri Lankan army were shocking. They say they were dragged screaming from their families and sent into action with only a few days of basic training. The older members of the LTTE warned them to keep firing and advancing, or they would be shot by their own side from behind.

Those who did try to escape said they were fired on by their own side. Children who were recaptured had their hair shaved off to mark them as deserters and boys were beaten.

Darchiga said she was shot in the stomach by the army two days after arriving on the front line, having been forced to pick up a rifle and go forward to fight. She said LTTE cadres left her bleeding for four hours before she received any medical treatment.

According to her testimony, the Tigers had warned every family that those children who could carry a weapon were expected to join up, regardless of age. Some as young as 11 and 12 had been taken, she said. "They told families that one child was enough. If they had five children, they would take four and leave just one."

She was taken to a training camp at Mullaivaikal, where nine days of basic military training were interrupted by frequent air attacks. On the morning of 24 March, she was sent to the front.

"I was scared and thought that I would die now and would never see my parents again. They had scared us and said we shouldn't sleep because the army would come and cut our throats."

She spent the first day hiding in a bunker, then she was shoved forwards because the senior Tiger cadres said they were running out of fighters. "They gave me a rifle. It was very heavy. They threatened us that we had to go forward and shoot; if we came back, they would shoot us themselves.

"I went a few hundred yards and hid behind a coconut tree. I saw the army coming and I was very scared and I was lying down trying to hide, but then they shot me in the stomach.

"I started screaming because of the pain, but the cadres told me to shut up because the army would hear me. They gave me a cloth to put on the wound. There was a lot of blood. It was four hours before they took me to the hospital at Matalan."

On 13 April she escaped and ran back to her family. The Tigers were looking for deserters, she said. "If they caught them, they shaved their hair off and sent them back to the front line." Boys also received a beating.

She finally managed to escape with a group of civilians, but only after the Tigers had fired on them. She was separated from her family, who were sent to the internment camps at Vavuniya, and taken to a court, which ordered her to be detained at Ambepusse for a year - the standard treatment for those who confess to LTTE membership, even if they had been coerced.

Ravindram Vajeevan, 17, said he arrived at Ambepusse on 9 April after escaping from the Tigers four days earlier. He had a large scar on his left arm where he had been shot by his former comrades as he ran away.

He had been taken from his family in Mullaitivu on 29 March, as fighting raged around the shrinking no-fire zone and LTTE numbers dwindled. A large group of men arrived at the house, he said, and dragged him from the bunker where he had been sheltering.

"They hit me and my mother was crying and I was crying, but they said I had to go to fight. My neighbours tried to stop them, but they said they would shoot. Then they fired in the air," he said.

He was taken to a camp with about 70 other young boys and taught how to make a bunker, how to handle a rifle, how to escape from an ambush and how to stage an attack. They were told that if they did not fight they would be shot from behind, he said. On the fifth day, he escaped.

"In the beginning, the LTTE were fighting for the Tamils, but in the end they were just fighting for themselves," he said.

Thambirasa Jagadiswary, 20, and her brother Thambirasa Thisanandan, 17, were reunited at Ambepusse after the the Tigers took them from their family. Jagadiswary was taken in June 2008 and drafted into a mortar unit before being captured; her brother was dragooned in February this year. He had spent 15 days with the rebels before escaping and surrendering.

Afterwards he was taken to Vavuniya with his parents. "They told us there that those who were in the LTTE should register, so I did," he said. "Then they told me they would separate us from our parents."

"I was talking with my friends when they brought him in," his sister said. "All of a sudden I saw my brother and I started crying and shouting and hugging him." Their mother remains in the internment camp at Menik Farm.

These teenagers' revelations come days after the UN human rights council rejected a call for an investigation into allegations of war crimes by both sides during the 26-year conflict and accepted an alternative Sri Lankan government resolution describing the conflict as a "domestic matter that doesn't warrant outside interference". The Sri Lankan military has also been accused of committing war crimes by firing on civilians.

Among the traumatised and unwilling child soldiers of the Tamil Tigers, there is just a desire for normality to return.

"I was one year with the LTTE and I must be one year here," said Jagadiswary. "Now I would just like to find my mother and get on with my life."