  Early rebrightenings at a post-burst time of 10^2 - 10^4 s have been observed
in the afterglows of some gamma-ray bursts (GRBs). Unlike X-ray flares, these
rebrightenings usually last for a relatively long period. The continuous energy
injection mechanism usually can only produce a plateau in the afterglow light
curve, but not a rebrightening. Also, a sudden energy injection can give birth
to a rebrightening, but the rebrightening is a bit too rapid. Here we argued
that the early rebrightenings can be produced by the ring-shaped jet model. In
this scenario, the GRB outflow is not a full cone, but a centrally hollowed
ring. Assuming that the line of sight is on the central symmetry axis of the
hollow cone, we calculate the overall dynamical evolution of the outflows and
educe the multiband afterglow light curves. It is found that the early
rebrightenings observed in the afterglows of a few GRBs, such as GRBs 051016B,
060109, 070103 and 070208 etc, can be well explained in this framework. It is
suggested that these long-lasted early rebrightenings in GRB afterglows should
be resulted from ring-shaped jets.
