KIZILYURT, Russia — With an automatic weapon at his side and a black flag behind him, the Islamic rebel explained why he had gone to war with his government. As is often the case in the broiling Muslim insurgency here in the North Caucasus, his complaints were intensely local: A police commander had announced a policy of harassing and threatening family members of suspected militants.

The rebel, Gadzhimurad Dolgatov, also known as Abu Dujana, who led the Kizilyurt cell of the Dagestan branch of the Caucasus Emirate, a much-feared insurgent group, caught the authorities’ attention. In December, he and six other rebels were killed by Russian forces in a spectacular raid involving hours of gunfire and several armored troop carriers.

Abu Dujana also apparently caught the attention of Tamerlan Tsarnaev, the older suspect in the Boston Marathon bombing, who had posted the rebel’s videos on his YouTube account. It is still not known if Tsarnaev, who was killed in a confrontation with the police, met Abu Dujana or other militants during a six-month stay last year in Dagestan, or if he was an admirer from afar.

On Wednesday, Tsarnaev’s mother, who lives in Makhachkala, Dagestan’s capital, faced a second day of questioning by U.S. investigators trying to determine exactly whom he met and what he did, and perhaps confirm the statement by his younger brother, Dzhokhar, who has been charged in the bombing, that they were not part of any organized terrorist group.

Still, it is clear from interviews with friends and relatives in Dagestan and in the U.S. that Tamerlan Tsarnaev had firm views about the violent split between moderate Sufi Muslims supported by the Russian government and adherents of Salafism, an orthodox form of Sunni Islam.

Tsarnaev sided squarely with the Salafist camp, which includes the jihadist rebels for whom violent revenge and score-settling are a way of life developed through years of anti-Russian insurgency. After the breakup of the Soviet Union, many of the Salafists studied at religious universities in the Middle East, forming a cadre of young ideologues.

Over the years, the Dagestan insurgency spawned its own ideological framework, based on Islam. In 1998, several mountain villages in Dagestan, in an area known as the Kadar Zone, rejected Russian law enforcement and courts and practiced Muslim religious law, called Sharia.

They were crushed by the Russian military in 1999, but the movement survived. Insurgents say they are fighting to uphold Islamic law and reject Russian institutions and practices, like women wearing revealing clothes and the sale of alcohol, and also to substitute for corrupt courts.