Police identified the victims who drowned in the sea off Newhaven, Phillip Island, as two women aged 20, a 23-year-old man and a 43-year-old woman.

They were all of Indian origin, according to Australia's High Commission of India.

Two off-duty lifeguards who were surfing in the area pulled three of the victims out of the water, while a rescue boat attended to the fourth.

All four were unconscious and unresponsive, with the man and two of the women dying at the scene.

The other 20-year-old woman was flown to a Melbourne hospital in critical condition but later died.

Their relation to each other was not confirmed as their family were still being informed, and the Indian High Commission in Australia said it was providing support to the victims' relatives and friends.

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Drowning area not patrolled

It is the state's worst beach tragedy since 2005 when five people drowned at Stingray Bay on the state's southwestern coast, Lifesaving Victoria said.

The organisation added that the area where the drowning occurred was not patrolled, though lifesavers are stationed in two neighbouring areas.

It urged anyone planning on going into the water off Phillip Island to stick to the area's patrolled beaches.

'Witnesses will recall it for rest of their lives'

Victoria Police Eastern Region Assistant Commissioner, Karen Nyholm described the incident as "horrific".

She said: "For those people that witnessed it... I'm sure it's something they will unfortunately have to recall for the rest of their lives."

Victoria Premier Jacinta Allan extended her condolences to the victims' families and reminded people to be "aware of local conditions" when visiting a place, adding that those "who know this area well don't swim there".

Police are investigating the incident, and the deaths are not being treated as suspicious.