The Israeli military says it carried out airstrikes on four Hamas targets in the Gaza Strip in response to mortar rounds fired at Israel.

The Gaza Health Ministry said three children and a 65-year-old Palestinian suffered light-to-moderate injuries in an airstrike that hit a metal workshop in Gaza City.

The military says it hit "terrorist infrastructure sites" early Thursday belonging to the Islamic militant group Hamas, which rules Gaza.

Palestinian media said an Islamic Jihad militant group outpost was also targeted.

Israel struck five other Hamas targets Wednesday, responding to a mortar shell launched toward Israeli forces near the Gaza Strip. The army said no soldiers were harmed.

Military spokesman Lt. Col. Peter Lerner calls it the "most serious" escalation since the 2014 war between Israel and Hamas.