A second senior commander of the militant Islamic Jihad group was killed overnight, Reuters reported on Sunday, amid continuing fighting between Israel and Palestinians that has seen some 30 Palestinians killed since Friday.

Commander Khaled Mansour was killed in an airstrike. His death follows that of another senior commander, Tayseer Jabari, who was killed on Friday.

In response, Islamic Jihad said it would “not let their blood dry before they bombard the settlements of the enemy,” according to Reuters. Palestinian militants fired rockets towards Jerusalem on Sunday, Reuters said, while Israel continued its attacks.

Israel said it launched its military operation on Friday to eliminate “a concrete threat” against its citizens.  

At least six children have been killed in the round of attacks, the BBC reported. The Israeli government denies responsibility for a strike that killed at least four children, claiming in a statement that the Islamic Jihad group had fired a rocket “that fell short and landed in Gaza.”

The Norwegian Refugee Council called for an immediate ceasefire as casualties rose on Sunday. “Every single escalation of violence in Gaza comes at the cost of ordinary people, who pay the highest price for military actions. We urge all parties to protect civilians by all means, put an end to hostilities and work towards an immediate ceasefire,” the organization said in a statement.

Gaza’s health ministry said more than 250 people have been wounded in the airstrikes, according to the Associated Press.