GAZA CITY, Gaza Strip (AP) — Israeli forces are moving deeper into southern Gaza, searching for a soldier who was apparently captured during a clash with Hamas militants earlier in the day. The forces are being backed by heavy tank fire and airstrikes.

More than 60 Palestinians and two Israeli soldiers have been killed today in fighting that quickly shattered a cease-fire brokered by the United States. The truce collapsed less than two hours after it began.

The Israeli Cabinet has been meeting in a rare Sabbath session to consider options, including whether to expand the 25-day-old operation against Hamas.

In Gaza's southern Rafah area, the Israeli military is urging residents in phone calls to stay indoors as troops advance.

Both Israel and Hamas accused each other of breaking the cease-fire, which had been announced by the U.S. and the U.N. and took effect at 8 a.m.

U.N. Secretary-General Ban Ki-moon blamed Hamas for violating what was meant to be a three-day humanitarian cease-fire. The U.N. chief demanded the immediate and unconditional release of the missing soldier.

An hour after the cease-fire began, Israel says, gunmen emerged from one or more Gaza tunnels and opened fire at Israeli soldiers. That's when the Israeli soldier, identified as Hadar Goldin, disappeared -- apparently taken back into Gaza through a tunnel -- while another two soldiers were killed.