Putin, Obama speak again amid probe into Tamerlan Tsarnaev

Boston bombing suspect Tamerlan Tsarnaev remains the focus of investigation in both Russia and the US, as authorities seek to learn how he became radicalized. Here are four other developments in the case. 

The wider ripple effects of the Boston Marathon bombings are showing up in US-Russia relations.

Presidents Vladimir Putin and Barack Obama talked by phone Monday, and they agreed to maintain close contact between their respective intelligence agencies and to work together on security matters of joint concern including the 2014 Olympics that Russia is hosting in Sochi.

Relations between the two nations have been strained of late, but the naming of two brothers of Chechen heritage as the key suspects in the April 15 Boston bombings, the Monitor reported earlier Monday, have opened the door to possible improvement, at least on the issue of countering terrorist threats.

But the forward-looking cooperation is occurring as some big questions remain about who knew what, and when, about the radicalization of Tamerlan Tsarnaev. The FBI identified him as a key suspect in the attacks, and he died April 19 after a gun battle with police, during which his brother also ran over him while trying to escape in a hijacked car.

US officials have said Russia in 2011 raised concerns with the FBI and CIA, separately, about possible ties of Mr. Tsarnaev to radical Islamist views. That has raised questions about the effectiveness of US law enforcement agencies at screening for potential terrorist threats.

Here are other recent developments in the Boston Marathon bombings case:

•FBI agents have visited the Rhode Island home of Tamerlan Tsarnaev's in-laws and carried away several bags, the Associated Press reported Monday. Katherine Russell, Tsarnaev's widow, has been staying there. She left with her attorneys through a separate door.

•Dzhokhar Tsarnaev, the other bombing suspect and Tamerlan’s 19-year-old brother, has been moved from a Boston hospital to a prison medical center outside the city. Whereas Tamerlan was in the US on a green card, Dzhokhar is a US citizen. Prosecutors are charging him with using a weapon of mass destruction – the two marathon-day bombs that killed three people and injured more than 200.

•The brothers’ parents, who are now in Russia but who lived in the US for much of the past decade, have backed off from any plans to travel to the US. Anzor Tsarnaev, the father, said that he believed he would not be allowed to see his surviving son, and that he is not feeling well, according to wire service reports. The body of his older son is unclaimed, and a spokesman for the state medical examiner told Reuters that the office is waiting to report autopsy results until someone claims the body.

•According to news reports over the weekend, Tamerlan Tsarnaev spoke to his mother, Zubeidat Tsarnaeva, about "jihad" in a 2011 phone call secretly recorded by Russian officials.

On Sunday Rep. Michael McCaul, chairman of the House Homeland Security Committee, said he believes that the bombing suspects’ mother played a "very strong role" in her sons' radicalization process. But the motives behind the attacks remain a matter on which investigators are still piecing together the full story.