<p>The invention relates to a catalyst system for polymerization of olefins, the catalyst system comprising a titanium-containing procatalyst carrying internal electron donor(s), an organoaluminium cocatalyst and a mixture of external electron donors, the mixture comprising a carboxylic acid ester or derivatives thereof, an alkoxy silane and a nitrogen based compound. The invention also relates to a process for polymerization of olefin(s) and to the polyolefin synthesized by the process.</p>
