As of 6am Friday, southern Riverina council areas will be switched from being in a green zone to an orange zone under Victorian government rules.

That means holiday-makers from outside the border bubble, such as Melbourne, will need to have a COVID test on their return south if they stay at places such as Albury, Corowa, Mulwala and Barooga.

The government noted the shift at coronavirus.vic.gov.au, stating "out of an abundance of caution, current green zone Local Government Areas in NSW (all located within the cross-border community) will become orange zones effective as of 6:00am on 2 July".

Increased unlinked coronavirus cases in Sydney have prompted the move.

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It does not affect those travelling within the border bubble from Victoria to NSW.

News of the switch came as the NSW government committed to assistance for southern Riverina businesses hurt by Victoria's May-June COVID lockdown.

Murray Regional Tourism chief executive Mark Francis was gutted by news of the border zone change.

"It's extremely disappointing and frustrating given it compounds the challenges for us already," he said.

"It places a higher importance on the NSW support package."

Mr Francis said he suspected it may lead to visitors deciding to make a dash across the border on Thursday night ahead of the moment the zone changes colour.