US prosecutors have charged 80 people over an international Internet romance scam that defrauded victims, many of them elderly women, of at least $6m.

The scam was run by two Nigerian men in the Los Angeles area who had help from associates in Nigeria and other countries, federal officials say. They operated fake online romances that solicited money from “vulnerable” women.

In one 2016 operation, a Japanese woman sent a total of $200,000 borrowed from friends and relatives to a “US army captain stationed in Syria” she met on an international site for digital pen pals. The fake military man, "Terry Garcia”, told the woman, referred to in court documents as “FK”, that he was stationed in Syria and had a plan to smuggle diamonds out of the country.

To avoid confrontation, he told her he could not use the phone while stationed in the country.

She was virtually introduced to his “associates”, including one who said he was a “Red Cross diplomat”, in the couple’s pursuit of the fake diamond smuggling. Additional requests for shipping costs and other details in the fake heist kept coming.

In pictures: US banker jailed by Russian court for fraud Show all 14 1 /14 In pictures: US banker jailed by Russian court for fraud In pictures: US banker jailed by Russian court for fraud 2019-02-15T185050Z-1041913715-RC11E657B970-RTRMADP-3-RUSSIA-BUSINESS-DETENTION.JPG Founder of the Baring Vostok private equity group Michael Calvey, who was detained on suspicion of fraud, reacts inside a defendants' cage as he attends a court hearing in Moscow, Russia February 15, 2019. REUTERS/Tatyana Makeyeva In pictures: US banker jailed by Russian court for fraud 07372543.jpg US investor Michael Calvey attends a hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. US investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud 1125031857.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Alexei Kordichev, chairman of the Board of Directors at PNB Banka (previously Norvik Banka), former chairman of the Board at Vostochny Bank (Orient Express Bank), suspected of large-scale fraud, ahead of a hearing at Moscow's Basmanny District Court. The court considers arresting Kordichev in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125022312.jpg Baring Vostok Investment Manager Maxim Vladimirov suspected of complicity in a large-scale fraud attends a hearing at Moscow's Basmanny District Court to consider his arrest in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125022291.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Baring Vostok Partner Vagan Abgaryan suspected of complicity in a large-scale fraud attends a hearing at Moscow's Basmanny District Court to consider his arrest in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 07372494.jpg US investor Michael Calvey (back C) is escorted to attend hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. US investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud urn-publicid-ap.org-93277d8c217f4568b96b8b1904b7e396.jpg Founder of the Baring Vostok investment fund Michael Calvey sits in a cage in the court room in Moscow, Russia, Friday, Feb. 15, 2019. A veteran U.S. investment fund manager has been detained in Moscow and faces fraud charges. A Moscow court said on Friday that Michael Calvey, founder and senior partner at Baring Vostok equity firm, was detained alongside two other fund managers. AP Photo/Alexander Zemlianichenko In pictures: US banker jailed by Russian court for fraud 07372493.jpg The Pervoye Kollektorskoye Bureau (First Collection Bureau) CEO Maxim Vladimirov is escorted to attend hearing on investigators' motion on his arrest in connection with Baring Vostok criminal case at the Basmanny district court in Moscow, Russia, 15 February 2019. U.S. investor Michael Calvey, senior partner at the Baring Vostok private equity funds, was detained in Moscow on fraud charges along with some other partners of the company, including business partner Maxim Vladimirov. EPA/MAXIM SHIPENKOV In pictures: US banker jailed by Russian court for fraud 1125031852.jpg Alexei Kordichev (C), chairman of the Board of Directors at PNB Banka (previously Norvik Banka), former chairman of the Board at Vostochny Bank (Orient Express Bank), suspected of large-scale fraud, ahead of a hearing at Moscow's Basmanny District Court. The court considers arresting Kordichev in connection with the criminal case against Michael Calvey, founder of the Baring Vostok Investment Fund. Sergei Bobylev/TASS In pictures: US banker jailed by Russian court for fraud 1125031860.jpg MOSCOW, RUSSIA - FEBRUARY 15, 2019: Michael Calvey, founder of the Baring Vostok Investment Fund, suspected of large-scale fraud, during a hearing at Moscow's Basmanny District Court. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 1125032009.jpg Michael Calvey, founder of the Baring Vostok Investment Fund, suspected of large-scale fraud, during a hearing at Moscow's Basmanny District Court. Sergei Bobylev\\TASS via Getty Images In pictures: US banker jailed by Russian court for fraud 2019-02-15T152441Z-650771727-RC114BA8B5A0-RTRMADP-3-RUSSIA-BUSINESS-DETENTION.JPG Founder of the Baring Vostok private equity group Michael Calvey, who was detained on suspicion of fraud, stands inside a defendants' cage as he attends a court hearing in Moscow, Russia February 15, 2019. REUTERS/Tatyana Makeyeva In pictures: US banker jailed by Russian court for fraud AFP-1DH711.jpg US investor Michael Calvey, the head of investment company Baring Vostok, detained on fraud charges, attends a court hearing in Moscow's Basmanny Court on February 15, 2019. - Russia has detained the US head of a major investment firm on suspicion of fraud along with several other people from the fund and other businesses, a court spokesperson told Russian news agencies. VASILY MAXIMOV/AFP/Getty Images In pictures: US banker jailed by Russian court for fraud 1125062626.jpg US investor, founder and senior partner at Baring Vostok, Michael Calvey (back), who is suspected of involvement in swindling 2.5b roubles from Vostochny Bank, attends a hearing at Moscow's Basmanny District Court into an application for a warrant for his detention; 5 Baring Vostok workers, including Calvey, and one Norvik Banka worker, have been arrested in connection with the ongoing probe into the fraud; Baring Vostok holds a controlling stake in Vostochny Bank. Sergei Bobylev\\TASS via Getty Images

"FK estimates that she made 35 to 40 payments over the 10 months that she had a relationship with Garcia,” a federal criminal complaint says. “During that time, the fraudster(s) emailed her as many as 10 to 15 times each day, and Garcia was asking her to make the payments, so she kept paying to accounts in Turkey, the UK and the US.”

Seventeen people have been arrested so far. Investigators say two key suspects living in Southern California oversaw the full operation, which attempted an additional $40m in theft. They were among the 17 arrested, but dozens of co-conspirators are still on the run.

All defendants face charges of conspiracy to commit fraud, conspiracy to launder money, and aggravated identity theft. Some will also face fraud and money laundering charges.

"We believe this is one of the largest cases of its kind in US history," US Attorney Nick Hanna said of the operation.

He told CNN that the online pleas for money weren’t limited to romance, and included schemes targeting businesses, including impersonating employees.