Authorities say a 27-year-old Kauai man posed as a photographer online to lure women and teens and force them into having sex with him.

Leonard Alpeche Jr. of Kapaa is charged with first- and third-degree sexual assault, kidnapping and 10 counts of extortion. He was being held at Kauai Community Correctional Center in lieu of $465,000 bail.

He pleaded not guilty to the 13 counts on Tuesday, said Kauai County Deputy Prosecutor Jake Delaplane.

Alpeche has been charged in connection with the sexual assault of one victim, a 24-year-old Princeville woman, who told authorities Alpeche forced her to have sex by threatening to release nude photos of her in October.

Alpeche allegedly lured the females by offering modeling opportunities for large sums of money for an exclusive underground modeling agency catering to anonymous wealthy people.

Police said the known victims are female Kauai residents, ranging in age from 13 to 27 years old. Alpeche allegedly developed relationships with them online, using several aliases. Police would not say whether charges involving other victims were forthcoming.

According to charging documents, Alpeche used similar methods of coercion involving at least six victims, dating as far back as 2006 and including a 2008 case in which he possibly impregnated a victim.

The victim in the October incident said she entered an agreement with a person she met on Facebook for a modeling session, the court document said.

The woman was asked to send photos of herself in a bikini and in the nude. She complied and was told to meet a photographer at Lihue Ball Park for her first modeling shoot.

On Oct. 27, the woman went to the park and met a man wearing a white scarf over his face who said he was the photographer.

After taking nude photos of the woman, the man said she would have to perform sex acts with him or he would release the photos to her family and friends, the document said.

In some cases, the victim was told to submit more nude photos, find another model to replace them, or submit to sex acts.