Six Hamas fighters were killed in an Israeli missile strike on Monday.
In one of Tuesday's attack, two Palestinian boys were killed and three others wounded when the Israeli army launched a missile.
A Palestinian health ministry official said the two boys - aged 11 and 12 - were in an area close to where fighters had fired rockets into Israel.
The Israeli army said it fired on two Palestinians standing next to a rocket launcher following a rocket attack by Hamas fighters.
Ongoing attacks
Earlier on Tuesday, an Israeli air attack killed three fighters from Islamic Jihad in the Gaza Strip near the border area.