motriti

1. (someone, something) to watch; to observe closely
   Policija danima motri njegovu kuću. — The police have been watching his house for days.
   Stajao je kraj prozora i motrio ulicu. — He stood by the window, watching the street.
2. (motriti na + acc.) to keep an eye on; to look after
   Motri na decu dok ja kupim karte. — Keep an eye on the kids while I buy the tickets.

Used both with a direct object (motriti nekoga) and with na + acc. meaning 'to keep an eye on'.