Updated

GAZA CITY, Gaza Strip -- Palestinian officials said an Israeli military strike killed four family members and wounded 13 others in the Gaza Strip on Tuesday after days of rocket fire toward Israel.

Three of those killed and most of the wounded in the late afternoon explosion at a house east of Gaza City were under 16, said Gaza Health Ministry spokesman Adham Abu Salmia. He said the fourth was 50.

TV footage showed body parts and shrapnel at the scene of the attack. Hamas said Israeli tank fire had hit the house in what would be the deadliest Israeli attack on Gaza in months.

The Israeli military said Palestinian militants had launched mortars against Israel Tuesday and the military shot at the source of the fire.

"Regrettably noncombatants were hurt, this is because Hamas attacks from civilian areas," the military said in a statement.

Israel hit a series of Palestinian militant targets in the Gaza Strip earlier Tuesday, damaging smuggling tunnels and suspected weapons sites. Palestinian officials said 19 people were wounded in those attacks. Palestinians bombarded Israel with dozens of mortars on Saturday in the largest barrage in years.

The border with Gaza was a frequent site of violence between Palestinian militants and Israeli forces but has largely been quiet since an overwhelming Israeli military offensive two years ago.

Both sides have largely honored an informal cease-fire since the 2009 war, in which about 1,400 Palestinians were killed, including militants and civilians. Israel says Hamas has since rebuilt its arsenal and a pattern of rocket attacks and Israeli reprisals has escalated in recent weeks.

Hamas immediately threatened to retaliate for the deaths of the four Gazans.

"The brutal crime of today will not pass without a response by the resistance," Hamas spokesman Ismail Radwan told The Associated Press. "Israel is escalating against our people and the whole world should show their responsibility to stop this escalation."

The military said it had no interest in further escalation. It said the attacks were in response to a barrage of 56 mortar shells and rockets fired by Gaza militants over the past week, the military said. The tunnels, it added, were meant for militants to infiltrate Israeli territory to attack civilians and soldiers.

A military statement vowed to "respond with determination" to any attempt to attack Israelis.

Abu Obeida, a spokesman for Hamas' militant wing, said Hamas had carried out the recent attacks in response to Israeli "aggression."

But he said the group remains committed to an informal cease-fire if Israel keeps things quiet.