A process for producing polyolefins, which includes polymerizing at least one olefin monomer, separating at least a part of the reaction mixture, dividing the separated reaction mixture into a polymer-lean fraction and a polymer-rich fraction, and subjecting at least a part of the polymer-lean fraction to a purification step prior to recycling back to the polymerization of at least one olefin monomer. The obtained polyolefins particularly have a low content of volatile low molecular weight compounds, a low content of low-molecular weight polyolefin waxes and a low content of residues derived from the catalyst employed.