A mystery donor giving $5 million to help children affected by the Christchurch earthquakes has no strong connection to the city but has visited in the past.

The wealthy philanthropist - with a strong interest in supporting at-risk youth - insisted on remaining anonymous after making the largest donation by an individual to the Christchurch Earthquake Appeal, which has now raised about $84m in total.

The donor was not seeking recognition and valued privacy, said appeal spokesman and NZX chief executive Mark Weldon.

Christchurch mayor Bob Parker said: "It's a huge gesture and it's mosty gratefully received"

Mr Weldon would not even disclose the person's gender or nationality because he felt it would be a "slippery slope" in creating further curiosity. He has previously told the Herald about 65 to 70 per cent of donations to the appeal were expected to come from abroad, with most from the United States, then London and Australia.

"The person wanted a lot of confidence that the money would be accurately delivered, and had a lot of questions around where it would go and wouldn't go," Mr Weldon said.

There was no family links or otherwise to Christchurch. The person had visited the city previously and had a "genuine level of concern for at-risk and underprivileged kids".

The $5m donation will be directed towards projects for school-age children in Christchurch's eastern suburbs, which have been hardest hit in the quakes stretching back to last September.

Projects would include facilities for indoor sports, safe indoor play and homework areas, Wi-Fi spaces, and a range supervised activities, Mr Weldon said.

"Another million dollar-plus donation has also been directed to this area. Combining these monies with other allocations from the trust will see a significant amount spent in the near term on a range of projects - large and small - in the eastern suburbs."

Christchurch East MP Lianne Dalziel said the donation was "fantastically generous".

She looked forward to seeing the money used to build a recreation centre for the youth, and a community centre kids could do their homework in.

Mr Weldon said the appeal had received about eight donations of around $1 million from individuals, and a few from corporations around the same level. One organisation gave $5m early on in the fundraising.

Fundraising would continue as long as it needed to, he said.