Yes. Suppose two opposite charged particles are at rest at a separation of l. As soon as they are released the particles start to move towards each other under the force of attraction and their velocities start to increase. So the kinetic energy of the system of these two particles which was zero initially (since u = 0) begins to increase because their velocities are increasing (K.E.= ½mv²). No external force is applied to this system of two particles even then the kinetic energy increases.
