Thomas Markle Sr, the estranged father of Meghan, Duchess of Sussex, has been arrested in the United States and charged with possession of child sexual abuse material.

The US Department of Justice announced that Markle, 82, was arrested in Lakeland, Florida, after law enforcement officers discovered sexually explicit photographs of him with prepubescent girls. The images were found in two storage units in the Los Angeles area that he had rented for nearly two decades.

FBI agents, acting on search warrants, searched the two units registered to Markle and found 78 items, including photographs, film negatives and books containing explicit imagery of him with underage girls.

An affidavit described three of those photographs. Two showed a man, identified by a witness as Thomas Markle, with a nude prepubescent girl. A third photograph showed a nude underage girl in what appeared to be a hotel room in the Philippines. Authorities also found photographs that appeared to show Markle with children in various stages of undress.

According to the Justice Department, authorities first learned in October that an individual had signed an affidavit stating they had discovered child sexual abuse material among Markle's possessions in the Philippines. Law enforcement then interviewed a separate individual who told them Markle had rented a storage unit near Los Angeles since 2008. Information gathered from the first individual led to the discovery of a second unit.

"Mr Markle allegedly targeted innocent children and sought to steal their innocence through his criminal actions," FBI Director Kash Patel said.

Thomas Markle was living in the Philippines earlier this year when he suffered a stroke and had his left leg amputated, which forced him to return to the United States.

Meghan issued a statement saying she first learned of the allegations against her father in 2018, when a letter detailing them was sent to the unit of London's Metropolitan Police that was handling her security at the time.

"I am deeply distressed at the news that has come to light in the last 24 hours," the Duchess of Sussex wrote. "My thoughts are with any children who may have been harmed."

"I hope it can now be understood that, despite certain media publications' distortion over the years, any distance from my father and my choice to not allow him to have contact with our children was for one reason: to protect them," she added.

Thomas Markle appeared in a Florida court on Friday. If convicted, the Justice Department said he could face a maximum sentence of 20 years in a US federal prison.

Meghan, Prince Harry and their two children, Prince Archie and Princess Lilibet, relocated back to the United Kingdom in August.