Iranian authorities on Saturday prevented the family of Mahsa Amini from holding a ceremony to commemorate the first anniversary of her death, confining her father under “house arrest”, as sporadic protests erupted nationwide despite heavy security, rights groups said.

Amini, a 22-year-old Iranian Kurd, died a few days after her arrest by religious police for allegedly violating the strict dress code for women in force since shortly after the 1979 Islamic Revolution. Her family says she died from a blow to the head but this is disputed by Iranian authorities.

Anger over her death rapidly expanded into weeks of taboo-breaking protests which saw women tearing off their mandatory headscarves in an open challenge to the Islamic republic’s system of government under supreme leader Ayatollah Ali Khamenei.

Mahsa Amimi’s father Amjad was detained early Saturday as he left the family home in the western town of Saqez, and then released after being warned not to hold a memorial service at her graveside, the Kurdistan Human Rights Network (KHRN), 1500tasvir monitor and Norway-based Iran Human Rights (IHR) said.

“Amjad Amini is under house arrest… Security forces are preventing him from visiting his daughter’s grave,” said IHR.

Read: Security forces intensify crackdown on Iran’s Kurdish area, four killed - rights group

Official news agency IRNA denied the reports of the father’s brief detention, and later said security forces had foiled an assassination attempt against him.

Amjad Amini was already summoned by intelligence officials last week after his announcement he planned to hold a memorial ceremony. One of Amini’s uncles, Safa Aeli, was detained in Saqez on September 5 and remains in custody.

Chokehold on dissent

Rights groups said security forces had blocked access to the cemetery in Saqez where Amini is buried and Kurdish-focused group Hengaw said a young man named Fardin Jafari was in a critical condition in hospital after being shot in the head near the cemetery. It was not immediately possible to confirm the report.

The protests sparked by Amini’s death lost momentum after several months in the face of a crackdown that saw security forces kill 551 protesters, according to IHR, and arrest more than 22,000, according to Amnesty International.

Iranian authorities say dozens of security personnel were also killed in what they describe as “riots” incited by foreign governments and hostile media.

Seven men have been executed after being convicted in protest-related cases.

Campaigners say the authorities have renewed their crackdown in the runup to the anniversary, putting pressure on relatives of those killed in the protests in a bid to stop them speaking out.

Read: Iran relaunches police patrols against veil violations: media

New York-based Human Rights Watch said family members of at least 36 people killed or executed in the crackdown had been interrogated, arrested, prosecuted or sentenced to prison over the past month with authorities imposing a “chokehold on dissent”.

With additional security forces sent to the area, Hengaw said people in western Iran were expressing discontent through a general strike, with shops closed in a dozen towns and cities including Saqez.

One of Iran’s most high-profile prisoners Narges Mohammadi, a prize-winning rights activist, and three other women prisoners meanwhile burned their headscarves in the courtyard of Tehran’s Evin prison to mark the anniversary, Mohammadi’s Instagram account said.

The New York-based Center for Human Rights in Iran (CHRI) said a fire broke out at Qarchak prison for women outside Tehran when security forces quelled a protest by inmates.

‘Take back Iran’

Witnesses in Tehran said there was a heavy security presence, with anti-riot police and security vehicles on the main streets and squares.

Persian-language channels based outside Iran, including Iran International, broadcast footage of residents shouting “Death to the dictator” and the main protest slogan of “Woman, Life, Freedom” from apartment blocks in Tehran and its satellite city of Karaj overnight.

Monitor 1500tasvir posted footage of dozens of people staging a daylight protest on Saturday on a street in the Gohardasht district of Karaj shouting “we will take Iran back!” and other slogans.

Similar gatherings were reported in the central city of Isfahan and the southern city of Shiraz. Hengaw published images of fires being lit on roads in the western city of Sanandaj and said security forces fired on protesters in Mahabad to the north.

Under the slogan “Say her name!”, Iranian emigres were holding commemorative rallies from Sydney to Toronto, with thousands in Place de la Bastille in central Paris chanting protest slogans and waving pre-revolutionary flags.