A process for polymerizing propylene in the presence of a polymerization catalyst comprising (I) a solid catalyst component comprising magnesium and titanium compounds and an internal electron donor; and (II) a cocatalyst comprising an aluminium alkyl and optionally an external electron donor, said process comprising the steps of: (A) continuously polymerizing propylene by introducing streams of propylene, hydrogen and said polymerization catalyst into a loop reactor at a temperature of from 65 to 100 °C and a pressure of from 25 to 100 bar to produce slurry of particles of a first homopolymer of propylene having a melt flow rate MFR 2 of from 3 to 20 g/10 min in a first reaction mixture; (B) withdrawing a slurry stream from said loop reactor, said slurry stream comprising said first reaction mixture and said particles of the first homopolymer of propylene, said particles further comprising said polymerization catalyst, and passing the slurry stream into a gas phase reactor; (C) continuously copolymerizing propylene by introducing streams of propylene, a comonomer selected from the group of ethylene and C4-C10 alpha-olefins and optionally hydrogen into said gas phase reactor at a temperature of from 65 to 100 °C and a pressure of from 10 to 40 bar to produce particles comprising a polymer mixture of said first homopolymer of propylene and a second copolymer of propylene, said polymer mixture having a content of comonomer units from 0.1 to 5 mol-% and a melt flow rate MFR 2 of from 1 to 10 g/10 min; wherein said polymer mixture comprises from 35 to 65 % by weight of said first homopolymer and from 65 to 35 % by weight of said second copolymer, and wherein the melt flow rate MFR 2 of said polymer mixture is lower than the melt flow rate MFR 2 of said first homopolymer; (D) withdrawing a stream comprising said polymer mixture from said gas phase reactor; (E) removing hydrocarbons from said stream withdrawn from said gas phase reactor to produce a polymer stream with reduced content of hydrocarbons and optionally introducing additives to the polymer mixture; (F) extruding said polymer mixture into pellets. (A) continuously polymerizing propylene by introducing streams of propylene, hydrogen and said polymerization catalyst into a loop reactor at a temperature of from 65 to 100 °C and a pressure of from 25 to 100 bar to produce slurry of particles of a first homopolymer of propylene having a melt flow rate MFR 2 of from 3 to 20 g/10 min in a first reaction mixture; (B) withdrawing a slurry stream from said loop reactor, said slurry stream comprising said first reaction mixture and said particles of the first homopolymer of propylene, said particles further comprising said polymerization catalyst, and passing the slurry stream into a gas phase reactor; (C) continuously copolymerizing propylene by introducing streams of propylene, a comonomer selected from the group of ethylene and C4-C10 alpha-olefins and optionally hydrogen into said gas phase reactor at a temperature of from 65 to 100 °C and a pressure of from 10 to 40 bar to produce particles comprising a polymer mixture of said first homopolymer of propylene and a second copolymer of propylene, said polymer mixture having a content of comonomer units from 0.1 to 5 mol-% and a melt flow rate MFR 2 of from 1 to 10 g/10 min; wherein said polymer mixture comprises from 35 to 65 % by weight of said first homopolymer and from 65 to 35 % by weight of said second copolymer, and wherein the melt flow rate MFR 2 of said polymer mixture is lower than the melt flow rate MFR 2 of said first homopolymer; (D) withdrawing a stream comprising said polymer mixture from said gas phase reactor; (E) removing hydrocarbons from said stream withdrawn from said gas phase reactor to produce a polymer stream with reduced content of hydrocarbons and optionally introducing additives to the polymer mixture; (F) extruding said polymer mixture into pellets. <EOS>