Washington, Apr 20 (IANS): The parents of the two Boston bombing suspects have flatly denied that their sons, Dzhokar Tsarnaev, 19, and his older brother Tamerlan, 26, could be involved in Monday's terror attack.

CNN Friday cited Anzor Tsarnayev, the father, as telling the channel in Dagestan, an area in volatile Russian Caucasus, that "someone framed them," while their mother, Zubeidat Tsarnaeva, said "this is a setup."

"It's impossible for them to do such things. I am really telling you that this is a setup," Tsarnaeva told state-run Russia Today from Dagestan, according to CNN.

"My son would never keep it in secret. ...If there is anyone who would know it would be me. He wouldn't hide it. But there was never a word."

The brothers came from the Russian Caucasus region and moved to Kazakhstan at a young age before coming to the US several years ago.

"My youngest was raised from 8 years in America. My oldest was really properly raised in our house. Nobody talked about terrorism," their mother said.

The suspects' parents recently returned to Dagestan in the Caucasus region after living in the US for about 10 years because they were "nostalgic," the father, Anzor Tsarnaev, told Russian state-run Zvezda TV as cited by CNN.

He accused someone of framing his sons. "I don't know who exactly did it. But someone did."

CNN citing a federal official said that Dzhokar Tsarnaev came to the US as a tourist with his family in the early 2000s and later asked for asylum.

He became a naturalised US citizen in 2012. Tamerlan Tsarnaev was not a naturalized citizen, said the official. He came "a few years later" and was lawfully in the US as a green-card holder.

Tamerlan Tsarnaev had studied at Bunker Hill Community College and wanted to become an engineer, according to those who knew him. He then took a year off to train as a boxer.

The official said that a posting on a social media site in the elder brother's name included the comments: "I don't have a single American friend. I don't understand them."

Dzhokar Tsarnaev attended Cambridge Rindge & Latin, a public high school, CNN said citing Eric Mercado, who graduated a year behind the suspect.

Larry Aaronson, Dzhokar Tsarnaev's neighbour and a former teacher at the high school Tsarnaev attended, called him a "wonderful kid."

"He was so grateful to be here, he was compassionate, he was caring, he was jovial," Aaronson told CNN.