A woman and three young boys have died in a horror car crash in the NSW Riverina.

NSW Police say the car crashed into a pole late on Tuesday night before rolling down an embankment into a water channel, landing on its roof at Yanco, about seven kilometres south of Leeton.

Everyone inside the car was dead by the time emergency services arrived around 11.15pm.

“Whilst yet to be formally identified the occupants are believed to be a 36-year-old woman and three boys aged 10, 11 and 12 who are all related to one another,” NSW Police said in a statement on Wednesday.

Officers from the Murrumbidgee Police District have established a crime scene that will be examined by specialist police.

Meanwhile, NSW Police are launching Operation Easter – a highly-visible traffic operation focused on reducing road fatalities and trauma this holiday weekend.

The five-day operation will begin at midnight and run until 11:59pm on Monday, with double demerits in place for drivers caught speeding, drink driving, not wearing seatbelts or helmets or using a mobile phone while behind the wheel.

Traffic and Highway Patrol Commander, Acting Assistant Commissioner Tracy Chapman, said substantial police resources had been assigned to the operation.

“The message is simple; drive to the speed limit, focus on the road – not your phone, and make sure you have a plan B if you are drinking,” she said on Wednesday.