The mother of Boston bombing suspect Dzhokhar Tsarnaev said he claims innocence in the attack that killed three people and injured more than 250 others at the finish line of last month’s Boston Marathon.

Zubeidat Tsarnaeva said her 19-year-old son told her in a phone call this week that he and his slain brother, 26-year-old Tamerlan Tsarnaev, are innocent of the April 15 bombings, despite authorities saying there’s strong evidence that the duo were behind the attacks and that Tsarnaev allegedly confessed to the attacks.

Dzhokhar Tsarnaev is being held in a federal facility that treats injured suspects and inmates; he is recovering from injuries he sustained in a shootout with authorities in Watertown, Mass., that left Tamerlan dead.

The suspect’s mother told the Associated Press that he had difficulty understanding what happened to him but said his condition is improving. Tsarnaev is now walking without a wheelchair, she said.

"He didn't hold back his emotions either, as if he were screaming to the whole world: What is this? What's happening?" Tsarnaeva told the AP in describing the only phone conversation she’s had with her son since the bombings.

Bloomberg News also reported on the call, but the media outlet’s story did not include Tsarnaev’s claims of innocence.

The Bloomberg News piece offered insight into Tsarnaev’s state of mind as Tsarnaeva recalled the conversation, which she said lasted about six minutes.

“I couldn’t stop myself from crying,” during the phone call, Tsarnaeva said earlier this week to Bloomberg News. “He said, ‘I am absolutely fine; my wounds are healing. Everything’s in God’s hands. Everything will be fine.”

The brothers’ father, Anzor Tsarnaev, also claimed that his sons had been set up.

"All I can do is pray to God and hope that one day fairness will win out, our children will be cleared, and we will at least get Dzhokhar back, crippled, but at least alive," he said.

Tsarnaev’s claim of innocence comes as the father of one of Tamerlan’s friends who was killed by the FBI last week, contended that his son was killed “execution style” by the bureau.

The friend, Ibragim Todashev, said he knew Tamerlan through their love of mixed martial arts in Boston. Initial media reports indicated that Todashev was shot and killed while being interviewed about the bombings and an unrelated unsolved triple homicide after he lunged at an FBI agent with a knife. Some reports said Todashev was about to sign a confession that he had a role in the September 11, 2011 triple murders in Waltham, Mass., when he attacked the agent.

But reports surfaced Thursday that Todashev was unarmed when he was killed. Authorities said it was “no longer clear” exactly what happened, according to the AP.

His father, Abdul-Baki Todashev, called the FBI agents who interviewed his son “bandits” during a press conference in Moscow where he showed photos of his son’s body taken in a morgue in Florida by a friend of his son. Ibragim Todashev moved to Orlando after living in Boston, and he was interviewed in Orlando last week by the FBI.

Reni Manukyan, Ibragim Todashev’s wife, told CBS News that she doesn’t believe the FBI’s account that the agent acted in self-defense.

"It's the way how they are saying he was protecting himself, that it was self-defense from the FBI agent," Manukyan said. "I don't think it is self-defense. You would not have shot him on the top of his head. It just cannot be true."

The circumstances of Todashev’s death are now under review.