A cluster of 35 coronavirus cases linked to a marriage ceremony near Sydney and new government measures have hit Australia's multi-billion-dollar wedding industry and forced many tearful couples to cancel the big day.

Restrictions on gatherings of more than 100 people were announced this week in a bid to stem the spread of the virus.

Among the new rules was the stipulation that indoor events should allow at least four square metres (43 square feet) per person, while the government has advised people to stay at least one metre away from one another.

The outbreak and new rules have thrown the wedding industry -- worth around Aus$4 billion (US$2.3 billion) a year in Australia -- into limbo.

"You're not just dealing with having to cancel an event... that people have been literally dreaming and thinking non-stop about," Sydney-based wedding planner Lara Beesley told AFP on Saturday. 

"It's very heartbreaking to see and there's been lots of teary phone calls."

From florists to photographers, those working in the industry were already feeling the impact as weddings were put off indefinitely, she added.

A total of 35 cases of the virus have now been traced back to the wedding south of Sydney earlier this month, health authorities said.

Groom Scott Maggs told the Sydney Morning Herald the discovery of a cluster linked to his wedding had come as a shock. "There was no hysteria or bans on March 6, it just wasn't on the radar," he said.

Couples are being urged to consider postponing or hosting smaller events, Elise James from wedding planning agency Easy Weddings said. "We're encouraging couples to do that where safe," she said.

Australia's confirmed cases climbed to more than 900 on Saturday, with seven deaths in the country since the outbreak began.