Iran, the world’s most prolific executioner after China, has hanged a woman and four men for murder in defiance of mounting criticism from human rights groups.

One of those executed in Tehran’s notorious Evin prison had killed a five-year-old boy while robbing his home. The woman was put to death for killing her husband after discovering he wanted to marry another woman, a government daily reported today.

Yesterday's hangings brought to 232 the number executions in Iran this year, compared to 317 in 2007, according to Amnesty International figures. China, a far more populous country, carried out 407 death sentences last year.

Human rights groups and European governments have criticised Iran for an increase in the number of hangings since authorities launched a clampdown on “immoral behaviour” in July.

Of particular concern is the number of youths facing execution for crimes they committed as children which has reached “crisis levels”, Amnesty International told The Times. There are “at least 132 juvenile offenders known to be on death row… although the true number could be much higher,” the organisation said.

Human rights groups accuse Iran of resorting excessively to the death penalty while Tehran counters that it is an effective deterrent used only after a thorough judicial process.

Iran’s national police chief, Esmaeil Ahmadi-Moqaddam, claimed at the weekend that the number of violent crimes, including murder, kidnap and armed robbery, had fallen by 50 per cent over the past two years.

Much crime is drug-related as Iran battles heavily-armed traffickers from neighbouring Afghanistan, Europe’s main supplier of heroin. Youth unemployment is another factor: many emigrate but some who cannot turn to drugs and crime.

The harsh political climate fostered under Mahmoud Ahmadinejad, the country's hardline president, also contributes to the high execution rate, analysts said.

“He’s a throwback to the early days of the (1979) Islamic Revolution and so you get the hardline social attitudes that go with the enforcement of Sharia law,” Michael Axworthy, an Iran analyst at the Institute of Arab and Islamic Studies at Exeter University, told The Times.

Capital offences in Iran include murder, rape, armed robbery, drug trafficking, adultery, treason and espionage.

Tehran is party to the International Covenant on Civil and Political Rights and the Convention on the Rights of the Child, which are international treaties outlawing the execution of those under 18 at the time of their crime. Iran has, however, attempted to circumvent its obligations by keeping minors on death row until they reach 18 and then executing them afterwards.

Behnam Zarei, a 19-year-old Iranian, was hanged in the south-western city of Shiraz on Tuesday after he had spent more than three years on death row for killing a fellow teenager.

Zarei, who was 15 at the time of his crime, had told the court the killing had been an accident. He was hanged “without the knowledge of his lawyer and family”, Etemad-e-Melli, an Iranian daily newspaper said.

He was the second youth in days to be hanged for an offence he committed as a child and the sixth such execution this year.

Human Rights Watch (HRW), a New York-based organisation, said Iran “leads the world in executing juvenile offenders”. At least 26 have been hanged since 2005, it added. No other country is known to have executed a juvenile offender this year.

HRW said: “Everywhere else, countries are moving to end this abhorrent practice, but in Iran the numbers of death sentences seems to be increasing.”

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