Updated at 3:45 p.m. ET:
Federal prosecutors have charged Khairullozhon Matanov with misleading the FBI and destroying evidence relevant to the investigation of last year's Boston Marathon bombing.
"He will plead not guilty," Ed Hayden, Matanov's court-appointed public defender told reporters. "Nothing he did or said was intended to mislead the FBI. And from what I know now, it didn't."
In an indictment unsealed on Friday, the U.S. attorney's office in Boston alleges that Matanov lied to investigators about his relationship with Tamerlan and Dzhokhar Tsarnaev, the prime suspects in the case, and attempted to wipe evidence off his computer.
"This is the most significant information that has come out on this incident since the initial arrests," Ed Davis, a former Boston police commissioner, told WBZ, the CBS affiliate in Boston.
Matanov, a 23-year-old resident of Quincy, appeared at a brief court hearing Friday afternoon.
According to the indictment, Matanov is a citizen of Kyrgyzstan who has been living in Massachusetts legally since 2010.
Hayden, his attorney, said Matanov came to the U.S. on a student visa and was later granted political asylum. He has worked as a cab driver and said he has no family in the U.S.
After entering the U.S., Matanov met and befriended Tamerlan Tsarnaev, who was killed during an altercation with police four days after the bombing. Matanov also knew Dzhokhar Tsarnaev, who was captured following a massive manhunt and is currently awaiting trial.
"Matanov participated in a variety of activities, including discussing religious topics and hiking up a New Hampshire mountain in order to train, like and praise the 'mujahideen,'" warriors who defend Islam, the indictment states.
Matanov tried to call both brothers in the hours and days following the Boston bombing on April 15, 2013, and saw Tamerlan in person at least twice, prosecutors say. Prosecutors say he had dinner with the Tsarnaev brothers the night of the bombing.
They accuse Matanov of making a number of false statements to federal investigators. The indictment states that he "deleted a large amount of information from his computer, some of which the FBI has been able to restore in an ongoing forensic review."
Prosecutors suggested recently that evidence suggests the Tsarnaev brothers did not act alone. Matanov is not charged with planning or carrying out the bombings themselves.
He was arrested early Friday morning. He faces one count of destroying evidence and three counts of making false or fraudulent statements.
If convicted, the maximum sentence for destruction of evidence is 20 years in prison, with the possibility of an eight-year sentence for each false statement count.