More than 600,000 vehicles were checked by cameras in the Hunter between March 1 - when fines started to be issued - and August 31.

The cameras caught 2649 drivers or riders in the Hunter - about one in every 230 drivers checked - illegally using a mobile phone.

The penalty for illegally using a mobile phone is a $349 fine ($464 in a school zone) and five demerit points.

The Hunter offence rate of 0.43 per cent over the period was higher than the state average of 0.23 per cent (or one in 432 drivers checked), Transport for NSW said.

"Simply taking your eyes off the road for longer than two seconds, doubles the risk of a crash," Transport for NSW deputy secretary of safety, environment and regulation, Tara McCarthy, said.

"Wherever a driver is on the road network, the message is simple: when it comes to mobile phones - get your hand off it.

"Those who think they can continue to put the safety of themselves, their passengers and the community at risk have been warned and will face consequences."

Transport for NSW did not reveal the number of cameras used in the Hunter during the six-month period, nor the amount of time they were operating.

While regularly sighted on some of the region's main roads and highways, the cameras are constantly moved to ensure their locations do not become known.

It is believed there are about eight cameras operating statewide, but the government plans to have 45 in operation by 2022-23.

Revenue NSW data shows 69,659 motorists were caught by the mobile phone detection cameras statewide, resulting in more than $31 million worth of fines.

All revenue raised goes towards the government's Community Road Safety Fund, which is used to support road upgrades, education programs and school zone flashing lights.

Both the Hunter and state offence rates were lower than the rate of offending during a six-month pilot conducted in the first half of 2019, when one in every 82 drivers (1.2 per cent) were caught using their mobile phone.

Mobile phone detection cameras are predicted to contribute to a reduction in road trauma of 100 fatal and serious injury crashes over a five-year period.

In NSW since 2012, there have been 183 casualty crashes involving a driver or rider using a hand held mobile phone - resulting in 13 deaths and 245 injuries.