The bodies weren't cold yet, fumes from the burning truck were still lingering over Stockholm city centre, when another war broke out - this time, online.

The Swedish far-right Internet swiftly responded to the terror attack of Friday (7 April) by laying the blame with the country's largest parties - the ruling Social Democrats and the centre-right Moderates that preceded them - and their migration policies that had brought Muslims into the country.

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Stockholm terror attack on 7 April triggered a wave of hate messages on internet. (Photo: TT News Agency/Anders Wiklund/via Reuters)

Some of the accusations, which quickly spread through social media, were illustrated with pictures of the victims. One showed the ravaged body of an 11 year old girl; her family's calls for the photographs to be taken down were in vain.

Others suggested that the attack, for which an Uzbek with Islamist sympathies has been arrested, was a "false flag" operation orchestrated by Swedish authorities. A widely circulated conspiracy relied on details that were later tracked down to sloppy reporting by the Daily Mail, a British tabloid.

Other lies were spread by politicians from the far-right Sweden Democrats (SD), the third largest party in Sweden, whose party secretary Richard Jomshof tweeted an edited image that claimed a priest had asked people to "forgive the terrorist". Jomshof eventually deleted the message but said that it didn't matter if it was fake, "the basic matter is the same".

But if the hateful remarks, lies and conspiracies were meant to divide people and pick political points on the terror, they may have backfired.

When Stockholm responded to the attack with the largest rally ever held in the Swedish capital, and thousands of people formed a human chain around the terror site, right-wingers started to lambaste them too.

"Something is really wrong with the Swedish people. They should be furious, instead they are thirsty for love," one far-right journalist complained.

Swedes also fought back against online hate by spreading messages of solidarity and support in the comment fields of media and Facebook.

"Hate spreads hate, so spread love," one woman wrote in reply to some remarks on the Facebook page of a Swedish newspaper, adding a heart.

"You're doing exactly what the terrorists want - you sow hate and fear," another added.

Others ended their posts with the hashtag #jagärhär, or #iamhere.

A love mob against racism

#Jagärhär is a closed group on Facebook.

It was created last May by Mina Dennert, a Swedish journalist with roots in the Middle East, who has said the amount of hate she faced on daily basis had made her "feel a bit smaller every year".

"We are not an opinion mob. Our success is not necessarily measured as getting others to change their views. Rather, the purpose of the group is to allow more people to make themselves heard and to facilitate good discussions without hate and threats," the group rules say.

#jagärhär doesn't tell people what to write; it's up to everyone to formulate a message.

Each day, group members link to a newspaper's comment section or social media page where egregious comments and personal attacks have started to take hold. Before long, hundreds of group members will have left friendly messages and appeals for a reasoned discussion in the face of hatred.

The method may sound prim, but it works.

After the terror attack, which marked the start of a particularly busy time for anti-hate vigilantes, the group managed to get many racist comments deleted, including some that were illustrated by pictures of the 11 year-old victim.

The love mob also backed up politicians and other people who suffered the wrath of racists.

"Am I allowed to write here? I just wanted to thank all the kind people who went to my Facebook page," wrote Magnus Betner, a comedian known for poking fun at racism, whose social media profile was covered in venom in the wake of the attack.

"I knew exactly what would happen and didn't feel like spending the weekend replying to criticism from people who refuse to listen, so I just didn't enter my page. Thanks to all of you who did it instead," he added.

The group itself wrote that it wasn't looking to defend the perpetrator of the deeds, nor to take political sides.

"We want to prevent that this tragedy is used to push through harder and colder policies, at odds with the warmth and compassion that Stockholmians and Swedes have shown during the last days," a moderator wrote in the group.

The rise of hate mobs

The internet has long been a place where hate against Muslims, women and sexual minorities has thrived, a problem that isn't unique for Sweden.

Fears that fake news and hate speech could propel support for xenophobic parties in the upcoming elections recently had the German government propose that sites which fail to delete slanderous content could be fined by up to €50 million. Berlin has also urged the EU to legislate against fake news.

But such calls have prompted concerns that any ban on fake news would just curb free speech. An idea doesn't die just because it has been deleted from Facebook.

While the discussion on how to legislate fake news could turn out barren, different private initiatives try to solve some of the problems.

Sleeping Giants is an organisation that calls on business to stop advertising with hate sites, in a bid to freeze their ad revenues.

In Germany, the Recht gegen Rechts (Right Against Right) foundation has launched a crowdfunding campaign - Donate the Hate - where people donate one euro to refugee and anti-far right programmes for each hateful comment posted online.

Such projects are still testing waters, but in Sweden, #jagärhär has already been described as a unique initiative that empowers people to make their voice heard.

The group is already widely known in Sweden because of its efforts and has quickly gathered more than 70,000 members who actively take part in the different calls. It has also launched English and German versions, #iamhere and #ichbinhier.

Dennert, the founder of #jagärhär, told EUobserver the group is in touch with Facebook and is pushing the social network to do more to remove what's illegal.

"In my lay view, the problem is not with the law but that it's not followed. Only a small part of all hate speech in Sweden is removed or registered with the police and investigated," she said.

The group should above all enable civic courage and discussion, she said.

"People feel good when they speak up when something is wrong. We feel good when we are there for each other," she said.

"Every time we act, a little bit of fear disappears. We are changing the world, one comment at a time. And we change ourselves."