Hamas says at least 13 Palestinians, including children, have been killed in the bombing of a mosque in the north of the Gaza Strip. It says 60 other people have been wounded in the air strike in Jabiliya. Israel carried out some 20 airstrikes on Gaza on Saturday and naval vessels are reported to have fired shells from the Mediterranean.At least 435 Palestinians have been killed in the offensive and more than 2,000 wounded. The UN says at least a quarter of the casualties are civilians. Hamas is warning that Israel would be defeated if it invaded Gaza, saying it would be a “black destiny” for Israel. The Islamist group called off a six-month truce last month, complaining about Israeli raids and a continuing blockade. Earlier on Saturday Israel killed a senior Hamas commander named as Abu Zakaria al-Jamal. He was the second Hamas leader killed in three days.