Synthesis of nanoscale particles as a result of vapor condensation under laser vaporisation of materials into high-pressure surrounding atmosphere has been studied. A 2D-hydrodynamic model is developed for a simulation of nanoscale particles formation in a laser-produced erosive flow propagating from the irradiated surface into the ambient gas. The analysis is based on a combined solution of the set of hydrodynamic equations describing the erosive flow and equations of nonequilibrium kinetics of particles nucleation and condensation growth. The detailed structure of the erosive jet is studied. It is shown that nucleation and condensation fronts are separated in space and are formed between the erosive vapor-gas flow and cold ambient gas. The model predicts bimodal particle-size distribution function. The particle size is shown to be independent on the evaporation rate and to increase with the laser beam radius and the ambient gas pressure.