Iran has executed six men found guilty of drugs smuggling, the semi-official Fars news agency reported today.

Murder, adultery, rape, armed robbery, drug trafficking and apostasy -- the renouncing of religion, in this case Islam -- are all punishable by death under Iranian sharia law practised since the 1979 Islamic revolution.

"Six narcotics smugglers with long past criminal records, who had been handed down separate execution verdicts, were hanged at Isfahan's central prison," Fars said, quoting judicial authorities in Isfahan province.

The verdicts were carried out after confirmation by the country's supreme court.

Since authorities launched a clampdown on "immoral behaviour" in July 2007, police have arrested dozens of drug addicts, smugglers, rapists and murderers.

Iran is going through its worst domestic crisis since 1979 Islamic revolution, with a series of protests by opponents of President Mahmoud Ahmadinejad that have turned violent.