MOSCOW — As dusk fell, nine young men gathered on a leafy street in Chertanova, a bedroom community on the outskirts of Moscow. Their hair cropped short, some put on surgical masks and thick work gloves. Aleksei Khudyakov, their leader, issued final instructions like a platoon leader briefing his soldiers for a raid.

“The dorms where they live are on the other side of the building,” Mr. Khudyakov, 25, explained as his cadre shuffled with anticipation.

“They” are the latest target of political and popular outrage here: unregistered immigrant workers, especially those from former Soviet republics like Uzbekistan and Tajikistan. And Mr. Khudyakov’s team intended to catch them where they slept.

“We’re going to go in,” he told the group, half warning and half pleading with them to refrain from violence or even foul language, “but we’re not going to be rude. I don’t want to see aggression.”