Pope Francis, in his strongest comments since the start of the conflict in Gaza, on Wednesday called for the release of all hostages taken by Hamas militants and said Israel has a right to defend itself.

Speaking in a sombre voice at the end of his weekly general audience to thousands of people in St. Peter’s Square, he also expressed grave concern over Israel’s siege imposed on Gaza.

“I continue to follow, with pain and apprehension, what is happening in Israel and Palestine. So many people killed, and others wounded. I pray for those families who saw a feast day turn into a day of mourning, and I ask that the hostages be immediately released,” he said.

“It is the right of those who are attacked to defend themselves, but I am very worried by the total siege in which Palestinians live in Gaza, where there have also been many innocent victims,” he said.

On Saturday, Hamas gunmen from the Gaza Strip rampaged through parts of southern Israel, in the deadliest Palestinian militant attack in Israel’s history.

Israel’s military said the death toll in Israel had reached 1,200 by Wednesday and more than 2,700 people had been wounded.