"The 15th chamber of the Islamic Revolutionary Court summoned Nazanin Zaghari this morning with her lawyer... to notify them of a new indictment," said the state TV website Iribnews, which cited "an informed source" and gave no further details.
Zaghari-Ratcliffe, who was convicted of sedition and jailed for five years in September 2016, was due for release in March 2021. She denies the charges.
The new indictment comes after her husband, Richard Ratcliffe, said late last month that he feared his wife could face a second trial.
"I think, behind closed doors, they keep saying there's a second court case, they keep talking about running it," he told British channel ITV.
Already in 2017, when Zaghari-Ratcliffe's family had hoped to obtain her early release, the Iranian Judicial Authority ruled out the possibility, saying there were "two cases" against her.
Zaghari-Ratcliffe was arrested at Tehran airport in April 2016 after visiting relatives in Iran with the couple's young daughter.
She worked for the Thomson Reuters Foundation -- the media organisation's philanthropic arm -- at the time.
Zaghari-Ratcliffe has been on temporary release from Evin prison in Tehran since the spring due to the novel coronavirus pandemic.
Media in both the UK and Iran have drawn a possible link between Zaghari-Ratcliffe's detention to Britain settling a debt dating back more than 40 years when the Shah of Iran paid the UK £400 million for 1,500 Chieftain tanks.
When the Shah was ousted in 1979, Britain refused to deliver the tanks to the new Islamic Republic but kept the money.
The British government has previously admitted it owes Iran up to £300 million ($395 million), but both countries have denied any link with the Zaghari-Ratcliffe case.
However, British daily The Guardian reported on Friday that UK Defence Minister Ben Wallace had for the first time acknowledged he was "actively" seeking to repay a debt to Iran to secure the release of Zaghari-Ratcliffe and other Iranian-British detainees.