Following the death of an 11-year-old boy in Spain from stabbing while playing football with pals, rumours circulated on social media that the suspect was either an unaccompanied juvenile seeking refuge or was originally from North Africa.

The toddler, whose family has given him the name Mateo, was attacked on Sunday morning when he and other kids were playing football at a sports complex in the small provincial town of Mocéjon. A man ran onto the pitch brandishing a sharp object while hiding his face with a scarf and a hood pulled over his head.

The victim’s family later suggested the attack was random, saying the man first approached another group of young people on the field who managed to slip away. He then caught Mateo, who was with two friends, reportedly stabbing him more than 10 times before fleeing the scene.

After police combed the area by land and air surveillance in an operation that stretched more than 30 hours, a 20-year-old man was arrested at his father’s house in Mocéjon in connection with the crime.

In the dozens of hours between the attack and the arrest, posts swiftly spread on social media making false assertions that the suspect was of North African origin or an unaccompanied minor seeking asylum in Spain, in an echo of the way that the murders in the English town of Southport were used to stoke anti-immigration tensions.

Among those who weighed in was Alvise Pérez, a 34-year-old far-right agitator from Seville who was recently elected to the European parliament. Pérez, whose political success was in part buoyed by his hardline anti-immigrant stance, drew a link on social media between the murder and the arrival of “50 Africans” at a hotel in the area. Pérez has been approached for comment.

As misinformation about the attacker’s identity proliferated online, the family of the victim pleaded with people to let the police do their jobs. “This has nothing to do with race or ideology,” a relative acting as a spokesperson for the family, Asell Sánchez, told reporters. “They’re talking about migrants who have come to the hotel, these are peaceful people who are getting on with their lives, it has nothing to do with this.”

Instead he pointed to evidence suggesting that the assailant had entered the sports centre via a broken back door, suggesting the attack had been carried out by someone who knew their way around the area.

Still, the misleading posts continued to rack up views, even as police sources made it clear in the Spanish media that they had ruled out any jihadist connection to the murder.

Sánchez later broke down in tears as he recounted how the misinformation had led to him becoming the target of online attacks.

“It’s been horrible,” he told broadcaster Cope. “I did this out of love for my family and I’m receiving criticism on social media, they’re attacking me. They’re investigating my past – I don’t have any kind of past, I’ve worked in media.”

His voice shook as he continued: “They’re pulling things out of context, they’re telling me that my hands are dirty because I have pictures [on social media] from Africa,” he said. “It’s been really difficult.”

A source with the hate crimes unit of Spain’s public prosecutor said they were looking into several of the messages that had been disseminated and which had sought to criminalise foreigners and “spark feelings of hatred, hostility and discrimination” against certain groups.

On Tuesday, one day after Spanish media broadcast images that appeared to show a young white man being arrested in connection with the crime, the Spanish government’s representative in the region of Castilla-La Mancha highlighted how misinformation had sought to play on people’s emotions in a case that had gripped Spain.

Milagros Tolón blasted those who had knowingly spread false claims, describing them as “sowers of hatred who had taken advantage of human suffering, such as the death of an 11-year-old child, to vent all their hatred on social media.”

Speaking to reporters, she characterised social media as a “dumping ground for filth”, as a cadre of mostly anonymous users look to lay blame on people over their skin colour or religion. Others aim to spread falsehoods simply for their own personal gain, she added, without going into further details.

“Can one be more cruel and wretched?” she asked. “I’m asking the hatemongers to be human and behave like human beings. Their misinformation causes harm and can provoke anger in innocent people,” she added. “You cannot take advantage of one tragedy to create another.”