BEREKEI, Russia — A handsome, new, white brick house, still lacking windows, sits deserted in the middle of this quiet agricultural village in Dagestan, the homeowner having slipped away midconstruction with his wife and three small children to join the Islamic State.

He was not the first. That came in January, soon after leaders of the long-running Islamist insurgency here in Dagestan, Russia’s southernmost republic, began pledging allegiance to the self-proclaimed caliphate in Syria and Iraq. Around 30 men and women, townspeople say, have melted away this year.

“When they lived here they were all followers of one extremist line of Islam, so when one left, he became an example and the others left, too,” said Capt. Abbas Karaev, 27, the village policeman, sitting in Berekei’s squat municipal building, a structure so dilapidated and dusty it appeared abandoned. “They were told it was a jihad in Syria, and they would go to paradise if they died in this war. That is all they had in their heads.”

Much like the disaffected Muslim communities in Europe, the Caucasus region and the swath of former Soviet republics across Central Asia have become a vital recruiting ground for the Islamic State. Law enforcement officials estimate that there are at least 2,000 fighters from the Caucasus among up to 7,000 recruits from Russia and the former Soviet Union now in Syria and Iraq.