ISLAMABAD (Reuters) - Pakistan on Tuesday hanged a man whose case triggered an international outcry after his lawyers said he was arrested as a juvenile and tortured into confessing to a murder.

Pakistan has hanged nearly 200 people since December, when a massacre by Talibanmilitants at an army-run school in Peshawar prompted the government to lift a de facto ban on capital punishment.

Only Iran and China have executed more people than Pakistan this year, says human rights group Amnesty International.

"Shafqat Hussain was this morning executed in Pakistan, despite widespread calls, both within and outside the country, for a stay," the legal aid group Justice Project Pakistan, which was representing Hussain, said in a statement.

An official at the Karachi Central Jail, where the sentence was carried out, confirmed the execution.

Pakistani law does not allow the execution of someone arrested as a juvenile, but state prosecutors say Hussain was an adult working as a watchman when he was arrested.

Lawyers for Hussain said school records showed he was 17 in 2004 when he was burnt with cigarettes and had fingernails removed until he confessed to killing a child.

His family have said he was 14; lawyers said the family did not keep records regarding Hussain's birth.

A Reuters investigation found that few of those executed by Pakistan have any links to militancy. Lawyers say the justice system is deeply flawed.

Few police officials are trained to conduct investigations and many are often accused of torturing suspects to confess. Defense lawyers, appointed by the courts for those too poor to pay, often do not show up.

Hussain's family says that is what happened to him.

"There are cigarette burns on his shoulder," his brother Manzoor told Reuters the day before Hussain was hanged. "They also burnt his ankles with a heated rod. Those scars are still there. You can go and see them."

His sister Sumera Bibi, 26, wept as Manzoor pointed out the spots where he said Hussain had scars.

"Why are we not getting justice from the government? We want justice," she cried. "We are pleading that my brother’s case should be tried all over again."

Their mother said the family only learned of Hussain's death sentence after his initial trial, adding that they were too poor to pay the 30,000 rupees ($300) a private lawyer demanded to fight the case.

She could only afford one trip to visit her son in all the time he was in jail, she said, and would not see him before he died.