  Accurate QED evaluations of the one- and two-photon interelectron interaction
for low lying two- and three-electron configurations for ions with nuclear
charge numbers $60\le Z \le 93$ are performed. The three-photon interaction is
also partly taken into account. The Coulomb gauge is employed. The results are
compared with available experimental data and with different calculations. A
detailed investigation of the behaviour of the energy levels of the
configurations $1s_{1/2}2s_{1/2} {}^1 S_0$, $1s_{1/2}2p_{1/2} {}^3 P_0$ near
the crossing points Z=64 and Z=92 is carried out. The crossing points are
important for the future experimental search for parity nonconserving (PNC)
effects in highly charged ions.
