A number of rightwing British activists have publicly praised mass murderer Anders Behring Breivik – one describing him as a "role model" – since the Norwegian extremist was sentenced.

Members of the English Defence League (EDL) and the National Front have voiced support for the 33-year-old, who was declared sane and convicted by an Oslo court nine days ago after killing 77 people in two attacks last year.

Kickboxer Darren Clifft from Walsall tried to garner support for a petition to free Breivik last week. The 23-year-old National Front supporter, who posts as "Daz MarxistHunter", left a message on Facebook stating: "[Breivik] is truly inspirational. He sacrificed his life so Europe might be free again from the clutches of Islam and cultural Marxism, multiculturalism and political correctness. I see him as my role model, what every European man needs to be in order for Europe to survive."

Another Breivik admirer, Nick Greger – who, along with EDL founder member Paul Ray, runs Order 777, which claims to bring together Christian resistance movements – wrote on Facebook that the Norwegian deserved a medal "for the groundbreaking performance to blow up his Marxist traitor government building".

Breivik detonated a bomb in Oslo on 22 July last year, targeting government headquarters before embarking on a killing spree on the island of Utøya, where young political activists had gathered for a summer camp.

Greger, a German former neo-Nazi, lives in Malta as does Ray, who reportedly fled the UK fearing arrest for inciting racial hatred.

Several EDL members also appear to offer support for Breivik, including Joel Yossi, a member of the EDL's Jewish division, who revealed that he had been writing to Breivik, who will be detained in Ila prison just outside Oslo for at least 21 years. Yossi wrote: "I have wrote letters to him in prison and he seems he is in high spirits."

The EDL leader, Stephen Lennon, has said that although Breivik's killings were "obviously wrong", the court has helped to legitimise his motives. Lennon states: "By saying that he was sane, it gives a certain credibility to what he had been saying. And that is that Islam is a threat to Europe and to the rest of the world." The EDL, with whom Breivik said he had links, says it is non-violent and opposed only to Islamic extremism.

Hope Not Hate, an anti-extremist group, said the sentiments of a small number of extremists helped to underline concern that the UK was "not immune" to a Breivik-style attack. The group's director, Nick Lowles, said the global network of counter-jihadist extremists meant the ideas that inspired Breivik were still being traded. "Sadly, there are many others at large who share his warped ideology. Seventeen people in the UK with far-right views have been imprisoned in recent years for terrorist-related offences," he said.

A report earlier this year found that 38% of BNP supporters considered armed conflict to be "always or sometimes justifiable". More than 48% believed it was either always or sometimes justifiable to "prepare yourself for conflict between groups" in order to defend the "national way of life".

Hope Not Hate has now set up a monitoring unit to track counter-jihadist activists that they hope will work as an "early warning system" to help identify potentially dangerous extremists. Lowles said it was vital that the government, police and security services began to devote the same level of resources as to other extremist threats.