Palestinian witnesses said at least 40 tanks were at the entrance to the Rafah refugee camp before dawn on Tuesday and that several had entered the camp, drawing gunfire from resistance fighters.
Occupation soldiers shot dead a 50-year-old civilian in the camp and critically wounded two fighters, one of whom died later from his injuries, said Palestinian medics.
Earlier two Israeli army officers were killed in an ambush by a Palestinian resistance fighter, said Israeli army officials.
The Palestinian was also shot dead in the incident at the Kissufim junction in the occupied Gaza Strip.
First reports said that the two Israelis killed were settlers. But a military spokesman said the information was revealed after the military censor had barred publication of the identities of those killed for several hours.
The resistance fighter opened fire at the occupation soldiers as they got out of a vehicle. He then threw at least one grenade, according to the Israeli spokesman.
The al-Aqsa Martyrs' Brigades, the armed wing of Palestinian President Yasir Arafat's Fatah group, and Islamic Jihad both claimed responsibility for the incident.