Forty days of protest in Iran passed on Wednesday, with demonstrators making it clear their demands for change are as strong as ever.

Tensions continued into Thursday, with anger over the death of at least one protester leading to attacks on official buildings.

In Mahabad, the death of 35-year-old Ismaeil Mauludi prompted chaotic scenes as protesters attempted to break into government offices. Norway-based human rights group Hengaw say he was killed by security forces during Wednesday’s demonstrations.

Protesters can be seen breaching the perimeter fence before dispersing in a hail of gunfire in this footage shared by Hengaw.

While municipal offices have been targeted before during these protests, it is rare to see demonstrations escalating in this way on video.

It follows mass demonstrations across the country on Wednesday.

The Kurdish city of Saqqez saw people taking to the streets early in the day.

It was the hometown and now resting place of Mahsa Amini, the 22-year-old woman whose death sparked the unrest that has swept across the country.

Huge crowds travelled to Mahsa’s grave to mark 40 days since her death, a significant milestone for Iranians as it marks the end of the traditional mourning period.

The Iranian forces attempted to dissuade people from gathering at her grave, but state-affiliated news reports denied that a large security presence had been assembled in the area.

However, videos posted to social media suggest otherwise.

The first part of the clip shows at least seven police officers dressed in protective gear and carrying anti-riot shields.

It appears to have been filmed on the western end of Madar Boulevard, which is located adjacent to one of the main roads leading to the cemetery in Aichi where many protesters were headed.

A larger group wearing the same uniforms appear to be gathered on the junction itself, but the video cuts off before we get a clear view.

Other pictures shared online show security forces gathered at Mydane Dayk Square, on the other end of Madar Boulevard, the previous evening.

Despite their efforts, thousands of Iranians came.

Iranian-backed media reports said 8,000 people marched to the cemetery. Figures provided by anti-government sources were much higher, saying some 35,000 men and women from nearby towns and cities attended.

It is difficult to report on the ground in Iran, but one online tool can provide an indication of how many people were travelling on the 2.85-mile main road from Saqqez to the cemetery.

One video filmed from a bridge almost halfway between the entrance to Saqqez city and the cemetery provides a 360-degree view of the crowd.

We have created a panorama by stitching together stills from the video to give us an image. This helps establish a snapshot view of the crowd on either side of the bridge as they walk back towards the city. It shows around 825m of the road.

Using this image, we can identify some key markers, such as a row of pylons along a trough in the ground and where the road curves around a grassy verge.

We then plotted these key markers onto the map supplied by mapchecker.com, a tool that provides an estimate of crowd sizes.

People in this snapshot are close together but are not standing shoulder to shoulder. There are also gaps and some cars. Using a guide provided by the site, we estimate that the crowd is standing 1.7 people per square metre.

Mapchecker.com estimates that the crowd visible in the snapshot is 14,535 people strong.

As we are unable to see beyond what is captured in the video, it is likely the true number of protesters is much higher.

The protest at the funeral appears to have remained calm, but tensions rose as the march returned to the city.

A video recorded on Wednesday afternoon shows the scene at Mydane Dayk Square.

Smoke billows from a police shelter that seems to have been set on fire by demonstrators.

Another fire can be seen burning in the square itself, while protesters watch on.

It is not clear exactly what is happening in this video as it is difficult to make out who the different groups are. However, the sound of weapons being fired can be heard at least once, which indicates that security forces are present.

Another clip posted online shows the chaotic scene on the ground in Mydane Dayk Square.

Protests on day 40 took place across the country, including the capital Tehran, Sanandaj, Gorgan, and Isfahan.

The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.