Israeli attacks on central Gaza killed at least 62 people including women and children, according to medical sources in the Palestinian territory.
The Israel Defense Forces (IDF) said they were investigating.
Earlier, the IDF said it began targeted operations al-Bureij in central Gaza and areas in the east of Deir al-Balah on Tuesday.
The IDF carried out airstrikes targeting military compounds and Hamas weapons depots, as well as underground infrastructure belonging to Palestinian Islamist group Hamas. "Several Hamas terrorists were eliminated in the attacks," the IDF said.
Israeli soldiers had previously deployed in al-Bureij at the beginning of the year, but later withdrew from the area. However, Hamas is still present in the densely populated area, the IDF said.
Residents of the two neighbouring refugee camps of al-Bureij and al-Maghazi told dpa on Wednesday that there had been uninterrupted attacks in the area throughout the night and that thousands of people had fled to the Nuseirat refugee camp nearby.
The IDF also continued operations in Rafah in the south of the coastal region, saying armed men who posed a threat to Israeli soldiers were killed.
