за ним наблюдают

they’re watching him

→ за
phrase Rare #45,704
they’re watching him The person doing the watching may be unspecified. The pronoun changes form to match the person being watched, as in «за ними наблюдают» (“they’re watching them”).
RU: За ним наблюдают уже неделю.
EN: They’ve been watching him for a week.