(Adds details of more letters sent from prison and comments from the Corrections Minister)
WELLINGTON, Aug 15 (Reuters) - The gunman accused of killing 51 people in New Zealand has written several letters from jail expressing his political and social views, prompting Prime Minister Jacinda Ardern to say that should never have been allowed.
The New Zealand Herald and other local media organisations had images of the six-page letter and envelope from the alleged mosque shooter, Brenton Tarrant, sent from Auckland Prison, which was posted online on the controversial image board 4chan.
"I think every New Zealander would have an expectation that this individual should not be able to share his hateful message from behind bars," Ardern was quoted telling reporters on Wednesday in Tuvalu, where she is attending the Pacific Islands Forum.
"Obviously, this is an offender who has a very specific goal in mind, in terms of sharing his propaganda, so we should have been prepared for that."
Prisoners are allowed to send and receive mail, and prison directors can only withhold it in certain circumstances.
Corrections Minister Kelvin Davis said on Thursday that Tarrant has sent nine letters from prison so far, two to his mother, five to others, while two were withheld.
Davis, however, said he did not have details about who the other five letters were sent to.
"I've asked corrections to look at the content of those other letters, but what we have done is we have put an immediate stop to any mail sent or received...," Davis told Radio New Zealand.
Tarrant also received "a couple of dozen" letters from around the world, Davis said, adding that some of them were withheld while others were sent through to him.
"We have made changes to the management of this prisoner's mail to ensure that our robust processes are as effective as we need them to be," New Zealand's Department of Corrections said in a statement.
New Zealand site Newshub said the last two lines of the letter posted on 4chan could be read as a call to arms but blanked out what it said.
Tarrant, an Australian, pleaded not guilty to 92 charges stemming from the massacre at two mosques in Christchurch on March 15. He faces trial on May 2020. (Reporting by Praveen Menon and Sonali Paul; Editing by Clarence Fernandez)