(Reuters) - An Israeli-American teenager accused of making dozens of bomb threats to Jewish community centers was identified for the first time on Friday in separate criminal complaints filed in U.S. federal courts in Florida and Georgia that linked him to hundreds of hoax calls in 2015 and 2017.

FILE PHOTO - An U.S.-Israeli teen who was arrested in Israel on suspicion of making bomb threats against Jewish community centres in the United States, Australia and New Zealand over the past three month, is seen before the start of a remand hearing at Magistrate's Court in Rishon Lezion, Israel on March 23, 2017. REUTERS/Baz Ratner/File Photo

Michael Ron David Kadar, 18, who has dual citizenship and lives in Israel, made at least 245 threatening telephone calls between Jan. 4 and March 7, many targeting Jewish community centers in the United States, according to the Florida complaint.

Kadar also appears linked to more than 240 hoax threats called into schools in the United States and Canada between August and December 2015, forcing thousands of students to be evacuated, according to the Georgia complaint.

Kadar, who is Jewish, has been in custody in Israel since his arrest there on March 23. His name had been withheld by Israeli authorities pending a formal indictment, which is expected within days.

U.S. and Israeli authorities have not offered a possible motive. Kadar's defense lawyer in Israel has told reporters he has a high IQ but the emotional intelligence of a 5-year-old.

Kadar's American-born mother said in an interview with Israel's Channel 2 that her son was home-schooled after he was unable to function in school due to a brain tumor.

"He's autistic," she said. "He can't control it. He can't think straight."

In the same interview, Kadar's father, who is Israeli, said, "To all the Jews in America, I want to say clearly, we are very, very sorry, from the bottom of our hearts." Both parents were filmed in silhouette to protect their identities.

The U.S. Justice Department did not say whether it would seek his extradition.

The waves of threats against Jewish groups forced widespread evacuations and prompted concern among Jewish leaders about a resurgence of anti-Semitism. Many Jewish community centers took steps to heighten security in response.

Authorities have said the calls also went to institutions in Australia, New Zealand and Canada.

THREATS AGAINST ORLANDO FLIGHT, SCHOOLS, HOME

The complaints against Kadar provided new detail about the evidence authorities have, including a flash drive found in his laptop containing recordings of numerous telephoned threats.

Kadar spontaneously told officers who arrested him at his house in Ashkelon, Israel, that he "did not do it," according to the Florida complaint. When asked what he meant, he referred to the Jewish community center threats, even though no officer had mentioned them, the complaint said.

Kadar also has a speech impediment that matched one observed in recordings of the calls, U.S. authorities said. He allegedly used masking technology to hide his location and disguise his voice.

It was not immediately clear why charges were brought only in Florida and Georgia, after Jewish centers in dozens of states were hit by Kadar's alleged threats.

The Florida complaint formally charges him with 15 threats, including against a United Airlines flight at Orlando's airport and several Jewish schools. In Georgia, he faces a single count for threatening a private residence in Athens, Georgia, in January, in part because he was not yet 18 when he made the 2015 school threats in that state and therefore cannot face charges as an adult.

In a statement, the JCC Association of North America praised the "leadership and determination" of Attorney General Jeff Sessions and federal investigators.

U.S. authorities previously made one other arrest in connection with the threats. Juan Thompson, a disgraced journalist, is accused of making several threats to Jewish organizations while posing as an ex-girlfriend as part of a revenge plot against her.

He has denied the charges.