Iraqi authorities have executed at least 11 people convicted of "terrorism" this week, security and health sources said Wednesday, with rights group Amnesty International condemning an "alarming lack of transparency".

Under Iraqi law, terrorism and murder offences are punishable by death, and execution decrees must be signed by the president.

A security source in Iraq's southern Dhi Qar province told AFP that 11 "terrorists from the Islamic State group" were executed by hanging at a prison in the city of Nasiriyah, "under the supervision of a justice ministry team".

A local medical source confirmed that the health department had received the bodies of 11 executed people.

They were hanged on Monday "under Article 4 of the anti-terrorism law", the source added, requesting anonymity due to the sensitivity of the issue.

All 11 were from Salahaddin province and the bodies of seven had been returned to their families, the medical official said.

Iraqi courts have handed down hundreds of death and life sentences in recent years for people convicted of membership in "a terrorist group", an offence that carries capital punishment regardless of whether the defendant had been an active fighter.

Iraq has been criticized for trials denounced by rights groups as hasty, with confessions sometimes obtained under torture.

Amnesty in a statement on Wednesday condemned the latest hangings for "overly broad and vague terrorism charges".

It said a total of 13 men were executed on Monday, including 11 who had been "convicted based on their affiliation to the so-called Islamic State armed group".

The two others, arrested in 2008, "were convicted of terrorism-related offences under the Penal Code after a grossly unfair trial", Amnesty said citing their lawyer.