People on social media are turning their profile avatars blue and posting blue-themed artwork in memory of 26-year-old Mohamed Mattar, who was killed during an attack by security forces in Sudan at the beginning of June.

The hashtag #blueforSudan has been trending internationally on Twitter as people seek to raise broader awareness of the situation in the country. The colour has been chosen because it was the Instagram avatar of Mattar, an engineering graduate.

The internet movement started when Mattar’s friends turned their profile pictures the same colour as the avatar on his mattar77 account.

Shahd Khidir, a Sudanese beauty influencer and blogger based in New York who has tens of thousands of Instagram followers, posted about his death last week, helping to widen the reach of the campaign.

Khidir told The Cut magazine that she wanted protesters’ voices to be heard in the face of an internet blackout in Sudan.

The #blueforSudan hashtag first started appearing in English on Twitter on 11 June, and by the following day had become a rallying point for Sudanese activists on social media to remember Mattar and to make a broader point about the situation.

Continued protests in the capital, Khartoum, have led to a violent crackdown by authorities in recent days. Doctors in Sudan have accused paramilitaries of carrying out more than 70 rapes during an attack on a protest camp in the capital last week. Social media users said Mattar was shot by forces while trying to protect two women during an attempt to disperse people from a protest camp.

Others who have encouraged the change include students at London Brunel International College, where Mattar had studied.

Many of the people using the hashtag have been posting it alongside a series of blue artworks symbolising the protests in Sudan. One of the most popular images is of Alaa Salah, the singing protester whose image went viral this year.

Another artwork repeatedly posted with the hashtag has been an image of a weeping woman, bearing the legend: “Please your life did not end here. You will be a part of a new history of a new era.”

The hashtag has become a rallying point for Sudanese nationals outside the country, with users encouraged to share statistics of victims of the government’s crackdown alongside the images.

A second image of a weeping woman, this time wearing Sudan’s national colours as her hijab, is also being widely shared.

As well as grassroots activists, celebrities including Demi Lovato and Naomi Campbell have joined in the trend.

Protests have been ongoing in Sudan since December 2018. Omar al-Bashir was ousted as president in April after three decades in charge and subsequently charged with corruption, but protesters say they will keep up their campaign until the military hands over power.