EU condemns Iran's flogging and jail sentence for rights defender
The details of both the verdict and the case against Mohammadi remain unclear.
"The EU calls on Iran to comply with its obligations under international law and urgently release Ms Mohammadi, taking also into account her deteriorating health condition," a spokesperson said in a statement.
The bloc said that enforcing the sentence "is against the universal principles of human rights and the rule of law."
A colleague of Nobel Peace Prize-winning campaigner Shirin Ebadi, who now lives outside Iran, Mohammadi has been repeatedly jailed by the Iranian authorities.
She was released from prison in October 2020 but then suddenly arrested again in November 2021 in Karaj outside Tehran while attending a memorial for a man killed during nationwide protests two years earlier.
Amnesty International at the time condemned Mohammadi's arrest as "arbitrary" and described her as a "prisoner of conscience targeted solely for her peaceful human rights activities".
Mohammadi, who has long campaigned against the use of the death penalty in Iran, had before her latest arrest been working with families seeking justice for loved ones who they say were killed by security forces in the 2019 protests.
Even while out of prison, she had in May 2021 been handed a sentence of 80 lashes and 30 months in jail on charges of "propaganda" against Iran's Islamic system.
Activists have decried what they see as increased repression in Iran in recent months, including the jailing of campaigners and greater use of the death penalty.
Prominent detainees have also died in prison, such as the well-known poet Baktash Abtin.