The Red Cross has called for Australians to donate blood amid concerns the deadly bushfires in New South Wales and Queensland will adversely impact the national supply.

Donor centres in New South Wales at Taree, Coffs Harbour, Port Macquarie and Byron Bay have been forced to close due to the fires.

Bushfires around Australia mean our centres in Coffs Harbour, Port Macquarie, Taree and Byron Bay mobile donor centre are currently closed. Our thoughts are with our colleagues and the community affected by these fires. We’ll update you when we can re-open the affected centres. pic.twitter.com/f5oTyd8xj7 — Red Cross Blood Au (@redcrossbloodau) November 12, 2019

It is estimated New South Wales and Queensland make up over half of Australia’s total blood supply.

Red Cross Blood Service spokesperson Helen Walsh said on Wednesday it was hoped the rest of the country could help fill gaps to ensure blood supplies stay strong.

“Given the unpredictability of the fires, the reality is we’re unlikely to immediately know the full impact on donations until later in the week,” Ms Walsh said.

“[But] we collect around 15 per cent of blood supplies for New South Wales in the areas where we have had to close our centres.”

“We are doing everything we can to support our regional customers with the potential need for increased supplies and the transfer of supplies interstate."

In addition to the centres already closed, the Red Cross expects appointment cancellations at its Maitland, Newcastle and Gosford centres, Ms Walsh said.

“With blood being a critical resource, we simply cannot afford to take a wait and watch approach and are calling for donors to please roll up their sleeves, now, in order to bolster the nation’s blood stocks.”

AAP

A strong southerly front on Tuesday night caused worsening conditions for firefighters battling "volatile" conditions in NSW, where three people have died and millions of hectares of land have been consumed.

The fire threat in Queensland was set to intensify on Wednesday, with strong winds and increased temperatures expected.

“Many people don’t realise the Blood Service is a truly national service with blood products shared around the country,” Ms Walsh said.

“So please, if you are eligible to donate, make an appointment at any blood donor centre in Australia and you will be helping maintain our stock levels in the face of these catastrophic fires.”

Call 13 14 95 or visit donateblood.com.au to find your nearest donor centre and book your appointment.

For the latest updates and current alert levels please visit the NSW Rural Fire Service website.