The Afghan, 22, wanted to target a football match or shopping centre, according to the Anti-Terrorism Prosecutor's Office in Paris.

The unnamed person was arrested on 8 October along with two other people in Toulouse and Fronton, southwestern France.

Sky's US partner NBC is reporting the person is related to Nasir Ahmad Tawhedi, 27, who was detained the day before by the FBI in the US state of Oklahoma.

Both Afghans are believed to have wanted to carry out the operations on behalf of Islamic State, according to officials.

Tawhedi is accused of plotting a violent attack with an assault rifle on behalf of the militant organisation, according to court documents.

They state he - along with a co-conspirator - expected to die as martyrs during the attack to coincide with next month's presidential election.

Officials also stated Tawhedi, who arrived in the US in September 2021, had recently ordered AK-47 rifles, liquidated his family's assets and bought one-way tickets for his wife and child to travel home to Afghanistan.

NBC News also reported he had once worked as a security guard for the CIA in Afghanistan.

Tawhedi's alleged co-conspirator was not identified by the Justice Department, which described him only as a juvenile, a fellow Afghan national and the brother of Tawhedi's wife.

Meanwhile French law enforcement officials confirmed they opened a preliminary investigation into a potential terrorist plot on 27 September.

On 8 October - the day after Tawhedi was arrested - an unnamed Afghan and two other individuals were detained in France.

"The investigations carried out revealed the existence of a planned violent action targeting people in a football stadium or a shopping centre instigated by one of them, age 22, of Afghan nationality," said a French law enforcement official.

They added that investigators found evidence that "establish[es] radicalisation and adherence to the ideology of the Islamic State".

Read more from Sky News:
IS-K linked to Taylor Swift terror plot
Yazidi woman kidnapped by IS freed from Gaza
North Korea accused of preparing to blow up border roads

An FBI affidavit does not reveal precisely when investigators became aware of Tawhedi, but reports what it says is evidence from recent months showing his determination in planning an attack.

A photograph from July included in the document depicts a man investigators identified as Tawhedi reading to two young children, including his daughter, "a text that describes the rewards a martyr receives in the afterlife".

Officials say Tawhedi also consumed Islamic State propaganda, contributed to a charity that functions as a front for the militant group and communicated with a person linked to recruiting people interested in extremism. He also viewed webcams for the White House and the Washington Monument in July.

Tawhedi has been charged with conspiring and attempting to provide material support to the Islamic State which - if found guilty - could lead to up to 20 years in prison.