The parents of Tamerlan and Dzhokhar Tsarnaev spoke at a news conference in Makhachkala on Thursday, repeating their certainty that their sons are innocent of the Boston Marathon terror attack.

“No,” said Zubeidat Tsarnaeva, mother of the two men whom authorities say planned and executed the bombings that killed three, injured more than 200 and exposed the vulnerability of a venerated annual event. “I don’t believe it, and I won’t believe it.”

Tsarnaeva addressed reporters after undergoing several days of interviews with U.S. intelligence officials and the Russian security services.

She said she was not unnerved by visits she received from FBI agents a year or two ago in Boston, in which they asked whether her elder son was inclined toward jihad or terror. Tamerlan, she said, had not expressed any such inclination.

“I didn’t see any reason to worry,” she said.

Tamerlan Tsarnaev was killed a week ago during a chaotic confrontation with police. Dzhokhar Tsarnaev was captured hours later after a massive manhunt that paralyzed much of the Boston region; he remains hospitalized and has been charged with murder and use of weapons of mass destruction in the Boston attack.

Russian authorities contacted U.S. officials in 2011 and raised concerns that Tamerlan Tsarnaev was seen as an increasingly radical Islamist who could be planning to travel overseas. Tamerlan Tsarnaev spent several months in Russia in 2012.

In congressional testimony Tuesday, Homeland Security Secretary Janet Napolitano said U.S. authorities had flagged Tsarnaev’s departure, but not his return. “By the time he returned, all investigations had been closed,” Napolitano said at a Senate hearing.

On Thursday, Russian President Vladimir Putin said Russia’s intelligence service “could not provide operative information” on Tamerlan Tsarnaev because he lived mostly in the United States. The family, who are ethnic Chechens, immigrated to the United States when Tamerlan was a young teenager.

Zubeidat Tsarnaeva and the suspects’ father, Anzor Tsarnaev, have moved to this town in the southern Russian republic of Dagestan. Anzor Tsarnaev told reporters he plans to travel to the United States on Thursday or Friday to try to see his surviving son and claim his other son’s body.

Zubeidat Tsarnaeva said the decision to immigrate to the United States had been a big mistake.

“Why did I go there?” she asked. “America took my children away from me.”

About the Tsarnaev brothers

Will Englund in Moscow contributed to this report.