Israel pressed on with its offensive on Rafah a day after saying its forces had taken control of a buffer zone along the nearby border between the Gaza Strip and Egypt, giving it effective authority over Gaza's entire land frontier.
It said the buffer zone's capture had cut off a route used by the Palestinian Islamist militant group Hamas to smuggle arms into Gaza during more than seven months of war, which has laid waste to much of the territory and raised fears of famine.
Gaza medical sources said the 12 Palestinians, whom it said were civilians, had been killed and an unspecified number of others wounded in an Israeli airstrike as they tried to recover the body of a civilian in the center of Rafah.
Another Palestinian civilian was killed in an airstrike on Al-Shati refugee camp west of Gaza City in the north of the densely populated enclave, the medics said.