  We present studies of universal properties of the chiral phase transition in
$N_f$=2+1 QCD based on the simulations using Highly Improved Staggered fermions
on lattices with temporal extent $N_\tau$=6. We analyze the quark mass and
volume dependence of the chiral condensates and chiral susceptibilities in QCD
with two degenerate light quarks and a strange quark. The strange quark mass is
chosen to be fixed to its physical value ($m^{phy}_s$) and five values of light
quark masses ($m_l$) that are varied in the interval 1/20$\gtrsim m_l/m^{phy}_s
\gtrsim$1/80. Here various quark masses correspond to pseudo Goldstone pion
masses ranging from about 160 MeV to about 80 MeV. The O(N) scaling of chiral
observables and the influence of universal scaling on physical observables in
the region of physical quark mass values are also discussed.
