SEOUL - Matthew Miller, the American held in North Korea since April for "hostile acts", began a six-year hard labor sentence on Thursday that he said involved farm work and isolation, media reports said.Miller, 25, said in an interview with the Associated Press he had written to US First Lady Michelle Obama, Secretary of State John Kerry and his predecessor Hillary Clinton asking for help."Prison life is eight hours of work per day," Miller, dressed in grey prison clothes and a hat, said in the video interview. "Mostly it's been agriculture, like in the dirt, digging around. Other than that, it's isolation, no contact with anyone."CNN also reported that a North Korean government official released a photo of Miller, taken on Wednesday, his head shaved and in grey prison clothes with the number 107 on his chest and staring away from the camera.North Korea's state media said on Saturday that he pretended to have secret US information and was deliberately arrested in a bid to become famous and meet Kenneth Bae, another American detainee in a North Korean prison.Reuters reported earlier that Miller spent months in South Korea pretending to be an Englishman named "Preston Somerset" and invested time and money hiring artists to help create his own anime adaption of Alice in Wonderland, the Lewis Carroll fantasy with which he seemed fascinated.Bae, a missionary of Korean descent, is serving a 15-year hard labor sentence after being convicted of crimes against the state last year.