Russia withheld "crucial" information from the United States on one of the suspects of last month's deadly Boston Marathon bombings, The Wall Street Journal reported.
Citing unnamed US officials, the Journal said on its website that the information consisted of text messages between the mother of Tamerlan Tsarnaev and a Russian relative.
Tsarnaev died in a shootout days after the April 15 twin blasts that killed three people and wounded more than 260 near the finish line of the race.
His younger brother Dzhokhar — a fellow suspect captured after an extensive manhunt — is in custody.
US officials learned of the texts, which the Journal said suggested Tsarnaev was interested in joining militant groups that Russia blames for attacks in the Caucasus, a week after the attacks.
The newspaper said one US official characterized at least one of the texts as "generally discussing jihad" but with no specific mention of terror plans.
US officials referred to these text messages as the most important in a series of missed signals between the United States and Russia, according to the report.
Several officials told the Journal that the details would have caused authorities to take a closer look at Tsarnaev.
After Russia alerted the Federal Bureau of Investigation in 2011 about Tsarnaev, in part due to the texts, the FBI requested more information three times -- but to no avail, the Journal said.
In the end, it took a week after Tsarnaev was identified for Moscow to supply the FBI with information about the texts.
The newspaper also reported that during Tsarnaev's trip to Russia's southern republic of Dagestan in 2012, security services there had their eyes on him, with Dagestani officials saying he tried to build contacts with radical rebel groups in the area and also met with an Islamist fighter.
A US official told the Journal that the Russians were still not cooperating fully and had yet to provide surveillance information from Tsarnaev's trip.
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