US man charged over child porn murder

Authorities say a US man strangled his cousin and her foster daughter after he was caught taking pornographic photos of the 10-year-old girl.

Fifty-eight-year-old Brian Farmer is being held on Thursday on $US2.5 million ($A2.7 million) bail on murder and child endangerment charges.

The Monmouth County Prosecutor's Office says Farmer was in 62-year-old Joan Colbert's apartment when he was caught photographing Veronica Roach on July 30.

Authorities say Farmer killed Colbert and the girl and fled.

Detectives say they discovered the pornographic photos on Farmer's mobile phone.

Officials say Farmer and Colbert were cousins. It's not known if Farmer has a lawyer.

Neighbours have said Colbert had raised the girl since she was an infant.