The Hamas-run health ministry in Gaza says Israeli strikes kill 67 people in the overcrowded city of Rafah.
Hundreds of thousands of people have fled to Rafah, at the southern edge of the Strip, after months of fighting in Gaza.
In Rafah, a doctor tells the BBC the "most popular question on people’s minds is, where can we go?".
UK Foreign Secretary Lord Cameron urges Israel to "stop and think seriously" before taking more action, as there is "nowhere" for people to go in Rafah.
Israel says it carried out a "wave of strikes" while rescuing two hostages from the second floor of a building in Rafah.
The Israeli military says Fernando Simon Marman, 60, and Louis Har, 70, are in "good medical condition".
Israel launched its operations in Gaza after Hamas killed more than 1,200 people on 7 October, and took 253 people hostage.
The Hamas-run health ministry in Gaza says more than 28,000 Palestinians have been killed and more than 67,500 injured since then.
