New York (AFP) - A new type of crime -- so-called "virtual kidnapping" -- is on the rise, with hundreds of cases in the past year, many among Hispanics, the FBI and New York police warned Tuesday.

In the scam, someone calls claiming to have kidnapped a relative and demanding a ransom.

"While no actual kidnapping has taken place, the callers often use co-conspirators to convince their victims of the legitimacy of the threat," authorities said in a statement.

For instance, the caller might claim to have kidnapped the victim's daughter and have a young woman scream for help in the background during the call.

Or the caller might claim a relative was injured in a car accident with a gang member, who won't allow him or her to go to the hospital until vehicle damages are paid.

The caller is usually ordered to stay on the phone until the money is wired.

"Most schemes use various techniques to instill a sense of fear, panic and urgency in an effort to rush the victim into making a very hasty decision."

"It's a massive problem," an FBI spokesman told AFP. "We are talking about hundreds and hundreds of these calls coming on in the last 12, 18 months."

Most of the perpetrators seem to be Hispanic men, often speaking with a Spanish-language accent, the FBI said, but "the problem affects all the populations in the city."

They say the calls typically come from area codes outside the city, sometimes from the US territory of Puerto Rico.

According to authorities, the caller generally demands the ransom be sent to a third party in Puerto Rico though a wire transfer company such as Western Union.