A Department of Environment and Heritage worker is believed to have been shot dead while attending a property 55 kilometres north of Moree.

Police confirmed a 51-year-old man had been killed at a property on the Newell Highway about 5.40pm on Tuesday.

Police say they arrested a 79-year-old Moree man at a nearby property without incident just before 11pm. He is assisting police with their inquiries at Moree police station.

A source at the department said the worker had been serving a notice on an elderly man at the property when he was shot.

The man was receiving the notice because he was suspected of illegally clearing vegetation.