American investigators have travelled to Dagestan to interview the bombers’ parents and to look for terrorist connections he could have established there.

Even as investigators into the Boston Marathon bombings zero in on the Chechen connection of the suspected bombers, a Russian daily claimed one of the suspected terrorists received training in neighbouring Georgia.

U.S. Secretary of State John Kerry said quite bluntly the senior Tsarnaev brother, Tamerlan, had been radicalised during his six-month visit to Dagestan and Chechnya last year.

“[H]e learned something where he went and he came back with a willingness to kill people,” he said during a visit to Belgium on Wednesday.

Tamerlan (26) and his brother Dzhokhar (19) set off two homemade bombs during the annual Boston Marathon on April 15, killing three people and wounding nearly 200.

American investigators on Tuesday travelled to Dagestan to interview the bombers’ parents and to look for terrorist connections he could have established there.

Meanwhile, a leading Russian daily said Tamerlan had received “terrorist training” in Georgia, a former Soviet state adjacent to Russia’s North Caucasus.

According to documents of the Georgian counterintelligence service obtained by the Izvestia, Tamerlan Tsarnaev attended “seminars” organised in Georgia in the summer of 2012 by the so-called “Caucasus Foundation” in collaboration with the Jamestown Foundation, which Moscow repeatedly accused of anti-Russian activities.

Citing reports by Colonel Irakli Garibashvili, head of the Counterintelligence Department of the Ministry of Internal Affairs of Georgia, Izvestia said the Caucasus Foundation was set up shortly after the 2008 war between Russia and Georgia “to recruit young people and intellectuals from North Caucasus for fomenting instability and extremist sentiments in Russia’s southern regions”.

The foundation invited “sympathisers” from Russia to workshops and seminars in Georgia, where they were “recruited and trained in staging terrorist acts”.

The mother of the Boston bombers, Zubeidat, said the FBI had “counselled” and “controlled” her son for several years and had ultimately “set him up”.

The Georgian Interior Ministry denied Tamerlan had attended any seminar in Georgia, while the Caucasus Foundation denounced the terrorist training allegations as “outright lies”. However, earlier this month, Georgia’s new Ombudsman told lawmakers that the government of President Mikheil Saakashvili had armed and trained a 100 exiles from Chechnya for terrorist operations in Russia. In August 2012, the Chechens clashed with the Georgian military over delays in their transfer to Russia, leaving 14 people dead. At that time Georgian authorities said government troops had battled militants who had crossed over from Russia. A new probe into the incident was launched after opposition won parliamentary elections in Georgia in October 2012.