Christchurch: Recognising broad trauma suffered from the Christchurch mosque shootings, New Zealand's government has doubled the budget for mental health support.

More than $NZ8.6 million ($8 million) will be distributed to meet demand for post-traumatic stress disorder treatment and other community needs, Prime Minister Jacinda Ardern said on Friday.

"We will be dealing with the trauma of this day for years to come," she said.

"As we mark six months since the horrific events of 15 March, we remember the remarkable community spirit and unity that was on display in the weeks that followed.