More than 773,500 cars were checked between December 1 and 7, and more than 3000 people were caught using their phones.

The world-first mobile phone detection cameras recently launched in New South Wales caught more than 3300 people using their phones while driving in their first week of operation – but the drivers caught will only be warned, not fined.

A total of 3303 drivers were caught using fixed and trailer-mounted phone-detection cameras in New South Wales between December 1 and December 7.

But the drivers caught with hands on their phones won't be fined – instead, they'll receive a warning letter in the mail for the first three months of camera operation.

Fines of $344 ($457 in school zones) and five demerit points will be enforced from March 1, 2020.

There are 10 fixed and mobile cameras in service on New South Wales roads at the moment, but 35 more will roll out over the coming years.