Detectives in Boston are looking further afield as they piece together their case against Marathon suspect Dzohkhar Tsarnaev.
The uncle of Boston bombing suspect Tamerlan Tsarnaev described his recent visit to Dagestan in Russia and his great shock at the attacks.
Both men were enrolled in a school in Dagestan, a neighbouring region that was drawn into Chechnya's violence during the 1990s.
A Chechen leader said the Tsarnaev brothers' "root of evil" is in the United States, not in Chechnya.
"The root of evil should be looked for in the United States," said Ramzan Kadyrov, the Head of the Chechen Republic.
"(The brothers) grew up and studied in the United States and their attitudes and beliefs were formed there. Any attempt to make a connection between Chechnya and the Tsarnaevs is in vain," he added in a post in the Instagram website.
Deceased Boston Marathon bombing suspect Tamerlan Tsarnaev spent six months overseas last year, travel documents obtained by NBC 4 New York reportedly show.
Tsarnaev flew from John F. Kennedy Airport in New York on 12 January, 2012, for Sheremetyevo, Russia, and returned to JFK on 17 July, the local NBC station reported.
The documents are said to show that the suspect was born on Oct. 21, 1986 and first entered the US on July 19, 2003.
Investigators hope to find out if he received any terror training while he was overseas.
There is no record that his brother Dzhokhar Tsarnaev, who is still at large, left the US, the report adds.
Boston bombing suspect Dzhokhar Tsarnaev posted links to Islamic websites and others calling for Chechen independence on what appears to be his page on a Russian language social networking site.
Abusive comments in Russian and English have flooding onto Tsarnaev's page on VK, a Russian-language social media site. VK has over 200 million users and is particularly popular in Eastern Europe.
On the site, Tsarnaev identifies himself as a 2011 graduate of Cambridge Rindge and Latin School, a public school in Cambridge, Massachusetts.
It says he went to primary school in Makhachkala, capital of Dagestan, a province in Russia that borders Chechnya, and lists his languages as English, Russian and Chechen.
His "World view" is listed as "Islam" and his "Personal priority" is "career and money".
He has posted links to videos of fighters in the Syrian civil war and to Islamic web pages with titles like "Salamworld, my religion is Islam" and "There is no God but Allah, let that ring out in our hearts".
Russia condemns all "terrorists" regardless of their nationality, President Vladimir Putin's spokesman said on Friday after US police shot dead a terror suspect who once lived in Russia.
"They all deserve to be rejected," spokesman Dmitry Peskov said, adding that Russia was awaiting official information from the US on the dead man and a suspected accomplice.
Boston bombing suspect Dzhokhar Tsarnaev attended a school in Makhachkala, the capital of Dagestan, in 2001, Reuters reported.
The school register pictured above names Tsarnaev as a pupil - number 11 on the list.
The registry states Tsarnaev is Chechen, entered the school in 2001, studied in the first grade and arrived from Kyrgyzstan.
Shocked friends of 19-year-old Boston terror suspect Dzhokhar Tsarnaev have described the student as "friendly", "chilled out" and "well adjusted", the Boston Globe reported.
Ashraful Rahman, who studied with Dzhokhar at the Cambridge Rindge & Latin School, reportedly described the alleged bomber as “just a normal guy, very chillaxed and very laid back.”
Another former classmate, Lulu Emmons, was quoted as saying: “He was normal. He kind of fit in with everyone. Not really close with anyone, but he was friendly. I sat next to this guy. I joked with him."
The teenager's wrestling coach Peter Payack told the paper: “Everybody loved him. He wasn’t a loner, the complete opposite. He seemed like one of the most well-adjusted kids on the team."
Dzhokhar's former teacher Larry Aaronson reportedly said: “If someone were to ask me what the kid was like, I would say he had a heart of gold. He was as gracious as possible."
Dzhokhar is currently the subject of a police manhunt in the city after his brother Tamerlan was killed.
The president of Chechnya, Alvi Karimov, said the two Boston terror suspects have "no relations" with the republic and suggested the brothers may have "turned bad" while living outside the region:
– President Alvi Karimov
The people who are suspected of committing crimes in Boston have no relations with Chechnya. The Tsarnaev family moved away from Chechnya many years ago to another region of the Russian Federation, then to Kazakhstan.
So they were not living in Chechnya as adults, and if they turned 'bad', those who brought them up should be held responsible.
The suspects' uncle, speaking to reporters in Montgomery, Maryland, said he was "ashamed" of Dzhokhar and Tamerlan Tsarnaev.
"Of course we're ashamed, they are children of my brother, who had little influence on them," he said.
"They've never been in Chechnya. Chechens are peaceful people."
"I say Dzhokhar, if you are alive, turn yourself in and ask for forgiveness."
"He put shame on the entire Chechen ethnicity."