Ten women have accused the actor and singer Jared Leto of sexual misconduct in a new BBC documentary and report, including several who were underage when they were assaulted, claims Mr. Leto has denied.

Four of the women who spoke to the BBC accused him of criminal behavior. One woman said Mr. Leto sexually assaulted her in a motel bathroom when she was 17; another said she had sex with Mr. Leto in California when she was 17, which would be statutory rape at the time.

One woman described “being groomed” by Mr. Leto and accused him of “making repeated sexually explicit phone calls” to her when she was 16. He later sent her a nondisclosure agreement, she said, to prevent her from talking about their relationship, which she refused to sign.

Mr. Leto has not been charged with a crime related to the accusations in the report.

Four other women also said they received “strange and often very sexual” calls from Mr. Leto when they were younger, according to the BBC report. The allegations in the documentary occurred between 2002 and 2016, when Mr. Leto was in his 30s and 40s. He is now 54.

In a short, emailed statement, Mr. Leto denied the allegations.

“I have never sexually assaulted anyone in my entire life,” he said. “These claims are absolutely and categorically false.”

In the documentary, the BBC obscured the faces of many of the women who accused Mr. Leto and did not use their real names. But it said it corroborated the women’s accounts with friends and family members, and reviewed pictures and messages that support the women’s accounts, the report said.

Two men who worked as crew members with Mr. Leto’s band, Thirty Seconds to Mars, told the BBC that Mr. Leto would invite teenage girls to his dressing room during concert tours, or to his house when he was recording music.

One woman told the BBC that Mr. Leto spotted her backstage at one of his shows in 2006, when she was 17, and asked an associate to get her number. They later had sex at his house in California. Mr. Leto was 35 at the time.

When she raised the issue of being below the age of consent in the state, Mr. Leto “just kind of shrugged it off,” she told the BBC.

The woman who said Mr. Leto assaulted her in a motel room said she first met Mr. Leto when he was visiting a store in Las Vegas where she worked. He invited her back to his hotel, but the address he gave her was for a “dingy gross motel,” she told the BBC. She had assumed they were going somewhere else, but instead “he called her into the bathroom so the pair could talk while he showered,” according to the BBC. “He then grabbed her hand and used it to masturbate himself,” it said.

Mr. Leto has faced other sexual assault accusations over the years, which he has denied.

He first rose to fame through his role as Jordan Catalano in the TV show “My So-Called Life” and as the frontman of Thirty Seconds to Mars, with his brother, Shannon Leto, in the 1990s. He won an Oscar in 2014 for best supporting actor for “Dallas Buyers Club,” and in recent years has appeared in action and comic-book films like “Blade Runner 2049” and “Suicide Squad.” He most recently played the skull-faced villain Skeletor in “Masters of the Universe,” which was released last month.