The social media strategies used by the accused Christchurch mosque shooter and Islamic State (IS) media are overlapping, says a Harvard researcher investigating online radicalisation.

New Zealanders went into mourning after a gunman attacked worshippers in two Christchurch mosques, killing 50 and injuring dozens more.

Grafton man Brenton Tarrant, 28, who is accused of livestreaming the attack, had in the days preceding it allegedly uploaded a 73-page manifesto through the same anonymous file sharing services used by IS to disseminate their propaganda.

Norwegian extremist Anders Behring Breivik, who killed 69 people on the island of Utoya in 2011, took a similar approach to justifying his acts.

Read more: ABC News (Australia)