Pakistan has executed a man convicted of killing a seven-year-old boy in 2004 when he himself was just 14 years old, despite international outcry over his sentence.

Authorities hanged Shafqat Hussain shortly before dawn at a Karachi prison, said Iqbal Hassan, an official of the prison judicial branch.

Hussain's brother, Gul Hassan, received the body and will take it to his native village somewhere in Kashmir, Mr Hassan said.

The deceased's relatives visited him for the last time on Monday night.

Hussain's execution had been stayed four times amid the controversy over executing someone who committed a crime as a minor.

After his last appeal failed, Hussain remained on death row for another month as Ramadan had begun. Pakistan halts execution during the holy fasting month.

Pakistan imposed a moratorium on executions in 2008, but then lifted the ban in December, after a Taliban attack on a military school in Peshawar killed 150 people, mostly children.

While some militants have been executed, other convicts have as well.

Human rights groups say Pakistan has about 8,000 people on death row.

They have criticised the government for restarting executions, saying police often use torture to elicit confessions - including Hussain's. Authorities have denied the allegation.

Amnesty International called the execution a "deeply sad day" for Pakistan.

"A man whose age remains disputed and whose conviction was built around torture has now paid with his life - and for a crime for which the death penalty cannot be imposed under international law," said David Griffiths, Amnesty International's South Asia research director.