  We consider the random-bond +- J Ising model on a square lattice as a
function of the temperature T and of the disorder parameter p (p=1 corresponds
to the pure Ising model). We investigate the critical behavior along the
paramagnetic-ferromagnetic transition line at low temperatures, below the
temperature of the multicritical Nishimori point at T*= 0.9527(1),
p*=0.89083(3). We present finite-size scaling analyses of Monte Carlo results
at two temperature values, T=0.645 and T=0.5. The results show that the
paramagnetic-ferromagnetic transition line is reentrant for T<T*, that the
transitions are continuous and controlled by a strong-disorder fixed point with
critical exponents nu=1.50(4) and eta=0.128(8), and beta = 0.095(5). This fixed
point is definitely different from the Ising fixed point controlling the
paramagnetic-ferromagnetic transitions for T>T*. Our results for the critical
exponents are consistent with the hyperscaling relation 2 beta/nu - eta = d - 2
= 0.
