Newly released emails reveal high level communications between Prime Minister Jacinda Ardern's office and Facebook bosses in the immediate aftermath of the Christchurch mosque attacks.

The correspondence, released to the Weekend Herald under the Official Information Act, highlights significant fears about material Facebook was set to release after the massacre, which police said was critical to their unprecedented criminal investigation.

In a statement, Ardern said Facebook kept in regular contact with her office in the days after the attacks, including a phone call between herself and Facebook boss Mark Zuckerberg.

The revelations come a day after accused gunman Brenton Tarrant