Tang Hai Liang, 36, had been convicted of trafficking 89.55 grams (3.2 ounces) of pure heroin and Foong Chee Peng, 48, had been found guilty of dealing 40.23 grams of the same illegal drug. Both are Singaporeans.

Singapore law allows the death penalty to be imposed by a court if the amount of heroin trafficked involves 15 grams or more.

The Central Narcotics Bureau said that both men had chosen not to apply for resentencing under a law that took effect last year which abolished the mandatory death sentence in some murder and drug trafficking cases under certain conditions.

"Both of them understood the consequences of their respective decisions," the bureau said in a statement, adding that they had been represented by counsel during the entire legal process.

The death penalty used to be mandatory in the city-state for crimes such as murder, firearms offences and drug trafficking above a certain volume. This left judges with no choice but to impose capital punishment upon conviction.

But parliament in November 2012 passed the legal reforms which took effect last year.

Under the new legal regime, those facing the death penalty are given the opportunity to ask for resentencing under certain circumstances.

Judges now have discretion to impose life imprisonment on a person convicted of murder if the individual did not intend to kill.

They can also impose a life term on a drug courier who cooperated with authorities in a "substantive way" or is suffering from an abnormality that "substantially impaired his mental responsibility for committing the offence".

Since the law took effect last year, nine convicts have applied for resentencing and have had their sentences reduced to life imprisonment, the Ministry of Home Affairs said in a separate statement Friday.

Human rights groups have called on Singapore to abolish capital punishment, carried out by hanging since British colonial rule.

But the government has rejected the calls, arguing death sentences for the most serious cases must remain as a crime deterrent.