MAKHACHKALA, Russia -- During a six-month visit to his Russian homeland last year, Boston bombing suspect Tamerlan Tsarnaev's parents have said, he spent his time reading novels and reconnecting with family, not venturing into the shadowy world of the region's militants.
But now, investigators are looking into a range of suspected contacts Tsarnaev made in Dagestan, from days he may have spent in a mosque in the capital to time spent outside the city, with a relative who is a prominent Islamist leader recently taken into custody by Russian authorities.
Emerging details of his time in Russia have not fundamentally altered a prevailing view among U.S. and Russian investigators that he had been radicalized before his visit. But there have been reports that he sought out contact with Islamist extremists, and was flagged as a potential recruit for the region's Islamic insurgency.
It remains unclear to what degree his months in Russia, which were punctuated by punishing attacks between police and insurgents, may have changed his perspective. But a Dagestan official, who said he was not in a position to confirm or deny reports of Tsarnaev's contacts, said it appeared that he intended to link up with militant Islamists -- but left having failed. "My working theory is that he evidently came here, he was looking for contacts, but he did not find serious contacts, and if he did, they didn't trust him," said Habib Magomedov, a Dagestan anti-terrorism commission member.
Tsarnaev was fatally wounded in Watertown, just outside Boston, after police confronted him in a stolen car. Police shot him several times, then he was run over by a car driven by his fleeing brother, Dzhokhar, his accomplice in the deadly April 15 bombing, authorities have said. The bombing killed three people and injured about 260 others.
The wounded Dzhokhar Tsarnaev was arrested the next day and remains in custody, charged in the bombing.
Tamerlan's widow, Katherine Russell, has hired New York criminal lawyer Joshua Dratel, who has experience defending terrorism cases, as she continues to face questions from federal authorities investigating the bombing. She has not been charged.
Russian investigators are also looking into Tamerlan Tsarnaev's interactions online and exploring whether he and a Canadian-born militant, William Plotnikov, may have been part of a larger group of diaspora Russian-speakers who mobilized online, under auspices of a Europe-based group, a law enforcement official said.
Unearthing what investigators have learned became more difficult two weeks ago, when President Vladimir V. Putin told reporters that, "to our great regret," Russian security services were unable to share operative information on Tamerlan Tsarnaev and his brother, Dzhokhar, that they could have shared with U.S. officials. Police in Dagestan have said Tamerlan Tsarnaev was not under surveillance.
Since then, an official from the Anti-Extremism Center, a federal agency under Russia's Interior ministry, confirmed for The Associated Press that operatives had filmed Tamerlan Tsarnaev during visits to a Makhachkala mosque whose worshippers adhere to a more radical strain of Islam, and scrambled to locate him when he disappeared from sight after Plotnikov was killed in a counterterror raid.
An official from the same unit told Novaya Gazeta newspaper that Tsarnaev had been spotted repeatedly with a suspected militant, Mahmoud Mansur Nidal, who was killed shortly thereafter in a counterterror raid.
What is certain, however, is that investigators are looking into time he spent with a distant cousin, Magomed Kartashov, founder of a group called Union of the Just, a Salafi religious organization that promoted civic action, not violence. Police recently detained Mr. Kartashov, whose relation with Tsarnaev was first reported in Time magazine, after he took part in a wedding procession that flew Islamic flags.
Federal Security Service agents visited Mr. Kartashov Sunday in a detention center to question him about his relationship with Tsarnaev, focusing on whether the two had shared "extremist" beliefs, said Mr. Kartashov's lawyer, Patimat Abdullayeva.
Ms. Abdullayeva said her client had discussed religious matters with his younger relative, but that he had been a moderating influence on the younger man, whose views seemed to be more radical. "Magomed is a preacher; he has nothing to do with extremism," she said.
As head the Union of the Just, Mr. Kartashov has led demonstrations protesting police counterterrorism tactics, which are often brutal in Russia, and calling for establishment of Islamic law, or sharia, in the region. At a rally in February, he aligned himself with antigovernment forces in Syria, saying, "We do not want secularism, we do not want democracy; we want the law of Allah," according to the newspaper Nezavisimaya Gazeta.
The time Tsarnaev spent with Mr. Kartashov may offer the first firm clues to his thinking during that period. Five men who spent time with both told Time that the younger man was apparently interested in radicalism well before he came to Russia, and that they tried to dissuade him from supporting local militant groups. Mr. Kartashov's group is mainly known for protests, including one targeting the United States late last year, after release of the film "Innocence of Muslims," that ended with a U.S. flag burning.
Shakrizat Suleimanova, Tamerlan Tsarnaev's aunt, said the men were third cousins and remembered each other from their childhood and regularly spent time together last summer, but added that Mr. Kartashov was "no kind of extremist, and spoke against any kind of killing."
Associated Press contributed.