Anders Behring Breivik, who slaughtered 77 people in Norway last year, has written to a far-right gang member in Germany charged with helping in a series of racist killings, calling her a hero of national resistance, a German magazine reported.
Der Spiegel weekly reproduced on Sunday part of the letter the far-right Breivik sent to Beate Zschaepe, charged this month with involvement in the murders of nine immigrants - including eight from Turkey - and a policewoman between 2000 and 2007.
Zschaepe was a member of an underground cell called the National Socialist Underground (NSU), which police discovered by chance about a year ago. Two other male members of the gang were found dead.
The case raised concerns that German authorities had underestimated for decades the far-right threat. Several top intelligence officials have resigned since media revealed documents possibly linked to the NSU had been shredded.
Breivik addressed Zshaepe as "Dear Sister", according to Der Spiegel, in his letter dated May 7, 2012 - a time when he was on trial in Oslo. "We are both among the first rain drops which indicate that there is a massive purifying storm approaching Europe," the letter read.
"We are both martyrs for the conservative revolution and you should be extremely proud of your sacrifice and efforts. Know that your sacrifice is being celebrated in northern Europe by tens of thousands of cultural conservatives," he wrote.
Breivik, who set off a bomb in Oslo before going on a shooting rampage on an island where teenagers were on a summer camp, was found sane by the Oslo court in August and jailed for the maximum 21-year term, although this can be extended. He saw himself as a warrior against Islam.
Der Spiegel also reported that Breivik called on Zaepsche to use her trial as a platform to espouse her views, as he had tried to do, but the magazine did not show that part of the letter.
In an interview with Der Spiegel, Federal Prosecutor Harald Range said he believed Zschaepe, who gave herself up, was involved in all the murders. The trio had "planned everything, organized everything and in the end carried out everything together", he said.
(Reporting By Madeline Chambers; editing by David Stamp)