Townsville residents in Queensland, Australia, have spotted crocodiles and snakes roaming the streets following "unprecedented" flooding.

Authorities were forced to open floodgates on the Ross River Dam on Sunday to relieve pressure as heavy rainfall caused landslides and power blackouts.

Authorities have warned that more heavy rainfall is expected on Monday, which could bring flash flooding that would put nearly 20,000 properties at risk.

Snakes and crocodiles have been spotted on residential roads in Australia after devastating floods hit the northern state of Queensland, following eight days of monsoon-level rain.

Environment minister Leeanne Enoch issued a statement warning residents that the reptiles could turn up in unexpected places due to extreme weather conditions.

"Crocodiles prefer calmer waters and they may move around in search of a quiet place to wait for floodwaters to recede," she said.

"[They] may be seen crossing roads, and when flooding recedes, crocodiles can turn up in unusual places such as farm dams or waterholes where they have not been seen before."

Queensland Premier Annastacia Palaszczuk has warned Townsville residents that flooding has not yet reached its peak as torrential rain continues. Ian Hitchcock/Getty Images

"Similarly, snakes are very good swimmers and they too may turn up unexpectedly."

Ms. Enoch also told residents to resist the urge to go near the creatures, telling them instead to "report it as soon as possible to the Department of Environment and Science."

Read more: Dozens of wild horses were found dead at a dried-up waterhole in Australia as the region continues to suffer from a record-breaking heatwave

Images posted to social media showed homes and cars submerged in waist-deep floodwaters, with crocodiles turning up in cul-de-sacs and snakes in trees.

"Croc out the front of my dad's place in Mundingburra, O'Reilly Street, Ross River Road end. Cannot stress it enough to stay out of the water," Erin Hahn said in a Facebook post.

Authorities were forced to open floodgates on the Ross River Dam in Townsville to relieve pressure on Sunday as unprecedented monsoon rains caused landslides and power blackouts. Some 1,900 cubic meters of water was sent gushing into the already inundated town.

The Queensland Bureau of Meteorology said in a statement: "Dangerous and high-velocity flows will occur in the Ross River Sunday night into Monday. Unprecedented areas of flooding will occur in Townsville. Expect access routes to be cut."

Australia's military deployed boats and helicopters to rescue people from their homes on Sunday and rescue efforts continue.

—Sky News (@SkyNews) February 4, 2019 Many people have sought shelter at nearby Lavarack military barracks and the Red Cross is also assisting with the response and recovery effort.

Queensland state premier Annastacia Palaszczuk has warned more heavy rainfall is expected in Townsville and the surrounding area over the next two days, which could cause flash flooding and put up to 20,000 properties at risk.

"It's basically not just a one-in-20-year event, it's a one-in-100-year event," she said.

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