More than 400 U.S. military servicemembers paid over $500,000 in a blackmail "sextortion" scheme orchestrated by inmates in South Carolina correctional facilities posing as women online, authorities said.

On Wednesday, agents from several military criminal investigative agencies served arrest warrants and summonses to those allegedly involved in the scheme as the first phase of "Operation Surprise Party," the Naval Criminal Investigative Service (NCIS) said in a news release.

In total, 442 troops from the Army, Navy, Air Force and Marine Corps paid more than $560,000, according to the release.

"This despicable targeting of our brave service members will never be tolerated," NCIS Director Andrew Traver said in the release. "We will not allow criminal networks to degrade the readiness of our military force."

Aided by civilians, the inmates used fake names and online personas to target troops through online dating sites and media forums to engage in romantic relationships with the goal of extorting them for money, officials said.

Once messages and racy photos were exchanged, the prisoners allegedly posed as the girl’s father or a police officer, telling the servicemember the girl was underage and the images were child pornography, before demanding payment.

“With nothing more than smartphones and a few keystrokes, South Carolina inmates along with outside accomplices victimized hundreds of people,” Daniel Andrews, an army investigator focused on computer crimes, said in a news release.

Victims paid out of fear of jeopardizing their careers and repercussions from their command, officials said.

Once the servicemembers wired the cash, a runner received the transfer and deposited the funds into a JPay account, a payment processing system used by inmates, the Military Times reported.

The South Carolina Department of Corrections has petitioned to end inmates' ability to use mobile devices in prison.

More than 250 people associated with the scheme are under investigation and could face prosecution.

It was not clear how the extortion ring grew or how long it went on.

Other scams involving the military involves compiling photos of military men and using them to start online romances with unsuspecting women before extorting them for money with threats of revealing personal information.