otpočeti

1. (+ acc.) to begin; to start
   Dve strane su otpočele pregovore u ponedeljak. — The two sides began negotiations on Monday.
2. (of an event) to begin; to start
   Sednica je otpočela tačno u deset sati. — The session began at exactly ten o'clock.
   Radovi na mostu otpočeće sledeće godine. — Work on the bridge will start next year.

More formal than početi; common in news language.