This contribution is concerned with the channeling of a relativistic laser pulse propagating in an underdense plasma, and with the subsequent generation of fast electrons in the cavitated ion channels. Specifically, we study the interaction of laser pulses of duration of several 102 femtoseconds, having their intensity Iλ2 in the range [1019; 1020]Wcm−2μm2 and focused in underdense plasmas, with electron densities n0 such that the ratio n0=nc lies in the interval [10−3, 10−1], nc denoting the critical density. The laser power PL exceeds the critical power for laser channeling Pch = 1:09Pc, Pc denoting the critical power for relativistic self-focusing. The laser-plasma interaction under such conditions is investigated by means of three dimensional (3D) Particle-In-Cell (PIC) simulations. It is observed that the steep laser front gives rise to the excitation of a surface wave which propagates along the sharp radial boundaries of the electron free channel created by the laser pulse. The mechanism responsible for the generation of relativistic electrons observed in the PIC simulations is then analyzed by means of a 3D test particles code. The fast electrons are thus found to be generated by the combination of the electron acceleration caused by the surface wave and of the betatron mechanism. The maximum electron energy observed in the simulations is scaled as a function of PL/Pc; it reaches 350 - 400 MeV for PL/Pc = 70 - 140.