The present invention relates to a continuous process for producing polymers at conversions ranging from 50% to 95% having a Mooney viscosity of at least 25 Mooney-units and a gel content of less than 15 wt. % containing repeating units derived from at least one isoolefin monomer, more than 4.1 mol % of repeating units derived from at least one multiolefin monomer and optionally further copolymerizable monomers in the presence of AlCl.sub.3 and a suitable proton source (e.g. water) or cationogen and at least one multiolefin cross-linking agent wherein the process is conducted in the absence of transition metal compounds and organic nitro compounds.