BOSTON -- Russian state security secretly recorded a phone call in 2011 between Tamerlan Tsarnaev, one of the Boston Marathon bomb suspects, and his mother in which they vaguely discussed jihad, a law enforcement source said Saturday.

Zubeidat Tsarnaeva -- the mother of suspects Tamerlan Tsarnaev, 26, who was killed in a shootout with police during the manhunt following the bombings, and Dzhokhar Tsarnaev, 19 -- also was recorded by the Russian wiretaps in another call chatting with someone in southern Russia who was under investigation by the FBI in an unrelated terrorism case, the source said.
Not until late last week did the FBI learn about the existence of the calls. None of the calls discussed specifics of any attack against America, the source said.
Word of the calls came as a team of investigators completed their search of a Massachusetts landfill where they believe Dzhokhar may have disposed of a laptop and bombmaking materials, according to the source. The laptop could contain clues as to whether the brothers received outside guidance or support.
At the prison medical center now treating Dzhokhar, FBI interrogators have continued questioning him, but he has cooperated little since a judge read him his Miranda rights at a court hearing in a Boston hospital last week, the source said.
Authorities said the brothers planted the pressure-cooker bombs that killed three people and injured more than 260 at the April 15 marathon.
The mother's possible influence on her sons' actions has come under new scrutiny.
Back in 2011, the Russians told their U.S. counterparts that they feared the mother and Tamerlan Tsarnaev were religious extremists bent on militancy. Consequently the FBI conducted only a cursory inquiry into the family, the source said.
Both Tamerlan and his mother ended up on a U.S. government terrorist watch list with 500,000-plus other names as a result of the limited information Russia provided.
In the phone call between mother and son that the Russians wiretapped, Tsarnaeva and Tamerlan Tsarnaev discussed his going to the Palestinian territories, as well as the subject of jihad, but in a general, "nonspecific" way, the source said. The Associated Press reported he dismissed the idea of traveling to the territories because he said he didn't speak the language there, Arabic.
Intelligence officials have also found text messages in which the mother discusses how Tamerlan is ready to die for Islam, two sources said.
The 2011 U.S. probe of mother and son came after the tip from Russia that Tamerlan Tsarnaev may have been preparing to leave the United States for travel to Russia to join unspecified underground groups.

The probe's scope was limited, under FBI procedures, and authorities closed the case that June, according to the AP.
A few months later, Russia again expressed worry about Tamerlan Tsarnaev and Tsarnaeva, and they were both added to the watch list.
In fiery interviews from Russia, Tsarnaeva has angrily denied that she or her sons are terrorists and called the marathon bombings a hoax.
At the prison medical center, Dzhokhar is jailed in a single-person cell with a small slot for prison staff to slide in meals.
Interrogators are intermittently trying to get him to provide more information. They had initially questioned him under a narrow public-safety exception to Miranda rights rules. But after the judge read him his rights, he all but stopped cooperating, two sources said.
To avoid further questioning altogether, Dzhokhar must unequivocally and clearly invoke his rights, legal experts say.

If he asks for a lawyer, no one can even ask him for two weeks whether he wants to cooperate, said Georgetown Law professor David D. Cole, an expert in criminal, constitutional and national security law. Under another rule, Cole said, if a suspect invokes his right to remain silent, interrogators must take a break before approaching again. In either case, the suspect must be reread his Miranda rights.
However, these restrictions essentially apply only if authorities want to use the statements against him in the criminal case, said Cole and Boston University law professor Tracey Maclin.
The experts said that if authorities just use the information to foil other plots, or gather evidence against another accused terrorist, they can question Dzhokhar pretty much all they want.