Thirteen animal activists have been charged after storming a poultry farm on the outskirts of Sydney and taking off with hens - a number of which died in the process.

Police allege the group was protesting alleged animal cruelty at the Lakesland farm, near Camden, yesterday when they the raided the property.

"A large group of protesters allegedly forced entry to the shed of a chicken farm on Mowbray Road and threatened the owner with bolt cutters," NSW Police said today.

The group refused to leave the property and put chickens in cages before fleeing.

The activists climbed fences at the Mowbray Road farm near Camden yesterday. Picture: 9NEWS (9NEWS)

Clutching cages to take the chickens in, they stormed the Lakesland property and took a number of hens. Picture: 9NEWS (9NEWS)

Some chickens died during the raid, police said.

Officers later stopped a Toyota Hilux nearby containing cages of chickens.

RSPCA investigators were also at the property on Thursday after receiving "disturbing footage" of hens at the property.

Inspectors interviewed the owner and counselled him on his legal obligations to provide for the welfare of the hens.

But an RSPCA spokeswoman condemned what unfolded at the property.

The group were protesting alleged animal cruelty at the property when the raid occurred, say police. Picture: 9NEWS (9NEWS)

A number of the hens died during the raid and subsequent arrests. Picture: 9NEWS (9NEWS)

"It makes it hard to do our job," Stefania Kubowicz told AAP on Friday.

She said trespassing was illegal and taking the hens "can further harm the birds".

Thirteen people - eight women, four men and a 17-year-old girl - were taken to the local police station and charged with animal cruelty.

One man, aged 46, was also charged with assaulting police, common assault and use an offensive weapon with intent to commit indictable offence.

Before the arrests, one of the NSW Hen Rescue campaigners told 9NEWS that they were making a stand to ensure the best for the laying hens.

RSPCA investigators were also at the property yesterday after receiving some anonymous "disturbing footage" of starving hens kept in horrendously overcrowded conditions, allegedly taken at the farm. Picture: Supplied (9NEWS)

One of the NSW Hen Rescue campaigners told 9NEWS they were working to ensure the best outcome for the hens. Picture: Supplied (9NEWS)

“We’re here today to say that we want the best thing to happen for these hens – not for them to be put down, not for them to treated as evidence or commodities, but for them to be rescued and given a chance," she said.

The 12 adults were given conditional bail to appear at Picton Local Court on August 14.

The 17-year-old girl was given bail to appear at a children's court also in August.