A Manhattan karate instructor pleaded guilty Thursday to sexually abusing four young girls and possessing a trove of child porn documenting the sick acts.

Hector Bencosme copped to five counts of use of a child in a sexual performance and four counts of sexual abuse in exchange for 10 years in prison as part of a plea deal struck in Manhattan Supreme Court.

Prosecutors say that Bencosme, 58, preyed on students as young as 10 years old inside his basement studio on Post Avenue in Inwood.

He told his victims that he needed to evaluate their bodies then groped and massaged them and photographed them topless, according to court papers.

“As a martial arts instructor, this defendant used his unfettered access to children to manipulate and abuse them,” said Manhattan DA Cy Vance Jr. in a statement. “Even more disturbing, however, is the pattern of abuse; he continued to exploit students 17 years after his conviction for virtually the same crime.”

He was convicted in 2001 of a similar crime involving a teen student in the same facility. He was out on bail at the time and fled to his native Dominican Republic before sentencing. The plea deal also covers the two-decades-old case.