A police officer is dead after being struck in the head, with what's understood to be an axe in Sydney's north west.

A suspect has been arrested on a property near Windsor in a semi-rural area known as Oakville.

As NSW Police Commissioner Andrew Scipione heads out to the scene 7News can confirmed that the wounded officer has died.

The attack happened around 4:30pm after police were called two hours earlier to a violent dispute between two neighbours.

According to several reports, one neighbour was firing arrows from his property, but this has not been confirmed, along with any news on whether arrests have been made.

Paramedics worked to save the officer, but he has been pronounced dead at Hawkesbury Hospital where commissioner Andrew Scipione will be meeting the officer's family soon.

A suspect is believed to have been arrested.

The officer's death brings the number of police who have died in the line of duty in New South Wales to 252.

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