Israel claimed responsibility for Wednesday's killing in Gaza of a Palestinian militant from a splinter group that Hamas is trying to rein in.
An Israel airstrike early Monday morning targeted a smuggling tunnel in Gaza in retaliation for a militant rocket attack on Israel.
After Gaza rocket attacks resulted in the first fatality since last year's war, Israeli warplanes carried out retaliatory air strikes on at least six targets overnight. Hamas is struggling to contain unaffiliated militants in Gaza.
After blaming Israeli agents for assassinating a Hamas official in Dubai on Friday, Hamas said it too could broaden the conflict beyond Israel and Gaza. But analysts are doubtful Hamas can pull it off.