The internal inquiries could help Israel challenge the work of a U.N. Human Rights Council commission of inquiry into possible war crimes committed by its forces and Palestinian militants in the 50-day conflict in July and August.
Israel has long accused the 47-member state council of being biased against it and says Hamas Islamists, who launched rocket attacks on Israeli towns, operated in residential areas and bear ultimate responsibility for Palestinian civilian casualties.
Major-General Dan Efroni, Israel's chief military prosecutor, has ordered the armed forces' investigative teams to look into a total of 99 Gaza war incidents, the military said.
A senior officer, briefing foreign reporters, said five cases in which criminal charges could be brought include an air strike of a Gaza beach on July 16 in which four boys were killed and tank fire on a school run by the United Nations Relief and Works Agency in the town of Beit Hanoun on July 24 in which 17 people died.
Israel's heavy bombardments in densely populated Gaza and a high civilian death toll there raised international alarm.
The Israeli military described the death of the children on the beach - it initially said naval shelling killed them - as a "tragic outcome", adding that Hamas fighters were the intended target.
It said the Beit Hanoun school was hit by errant fire and the area around the facility had been used by militants to launch rockets. During the war, weaponry was found by the U.N. in three of its schools, but not in the one in Beit Hanoun.
The officer said the military was also looking into incidents in which other U.N. facilities were apparently hit, and that in all of its investigations it hoped to gather testimony from Palestinian witnesses with the help of international organisations working in Gaza.
The officer said the other criminal probes launched by the armed forces were examining the fatal shooting of a Palestinian woman outside the battle zone, an alleged assault by troops on a teenager and the suspected theft of money from a Gaza home.
No decision had yet been made on whether to open a criminal investigation into the heavy shelling that killed 150 Palestinians in the southern Rafah area on Aug. 1 after the suspected capture of an Israeli soldier, the officer said.
More than 2,100 Palestinians, most of them civilians, were killed in seven weeks of fighting, according to the Gaza health ministry. Sixty-seven Israeli soldiers and six civilians in Israel were killed.
Hamas, which is regarded by the West as a terrorist organisation and drew international condemnation of its rocket strikes against Israeli civilians, called the internal Israeli investigations worthless.
Israel launched its Gaza offensive on July 8 with the declared aim of halting the cross-border rocket salvoes by Hamas, the dominant militant group in the enclave.