At least 31 civilians have been killed by Iranian security forces in the crackdown on protests that erupted over the death of Mahsa Amini after her arrest by the morality police for not wearing a hijab, an Oslo-based NGO said on Thursday.

Earlier, Kurdish rights group Hengaw said 15 people had been killed in Kurdistan province and other Kurdish-populated areas of the north of Iran, including eight on Wednesday night.

With no sign of the protests easing, authorities restricted access to the internet, according to accounts from Hengaw, other residents, and internet shutdown observatory NetBlocks.

Hengaw posted a video where heavy shooting can be heard during a protest and accused security forces of “using heavy and semi-heavy weapons against civilians” in the northwestern town of Oshnavieh, according to a Reuters report.

Protests first erupted over the weekend in the northern province of Kurdistan, from where Amini originated, but have now spread across the country. Videos have gone viral in which women are seen to be playing a leading role in the demonstrations, waving and burning their veils, with some publicly cutting their hair in a direct challenge to clerical leaders.

IHR said its toll included the deaths of 11 people killed Wednesday night in the town of Amol in the northern Mazandaran province on the Caspian Sea, and six killed in Babol in the same province.

Meanwhile, the major northeastern city of Tabriz saw its first death in the protests, IHR said.

Officials have denied that security forces have killed protesters, suggesting they may have been shot by armed dissidents.

Meanwhile, Iranian President Ebrahim Raisi said on Thursday that “acts of chaos” are not acceptable, in a warning to protesters.

Speaking at a news conference on the sidelines of the United Nations General Assembly in New York, Raisi added he had ordered an investigation into the case of Mahsa Amini.