Israeli helicopters have fired missiles at targets in the Gaza Strip.
One the Israeli missiles struck an Islamic centre in Jabaliya
The overnight strikes on three locations came after a woman in Israel was killed by a rocket fired from the Gaza Strip on Thursday.
Meanwhile Palestinian leader Mahmud Abbas arrived in Gaza to hold talks with armed groups, in an attempt to put an end to militant attacks.
An upsurge of violence in recent days has put further strain on a fragile five-month truce.
The al-Aqsa Martyrs' Brigades and Hamas said they carried out Thursday's rocket attack, in revenge for the killing of an Islamic Jihad leader by the Israeli army in Nablus.
One of the missile fired by the Israeli helicopter gunships was aimed at a pro-Hamas Islamic cultural centre in Jabaliya, north of Gaza City, witnesses said.
Another was aimed at a cemetery near Khan Younis further south - from where militant have in the past launched rocket and mortar attacks on nearby Israeli settlements.
Witnesses said the third target was close to the Deir al-Balah refugee camp in central Gaza.
There were no immediate reports of casualties.
Violence escalated on Tuesday, when an Islamic Jihad militant killed five Israelis in a suicide bombing in the Israeli coastal resort of Netanya.
Israel responded by carrying out raids in Nablus.
This in turn triggered Thursday's rocket attacks by al-Aqsa Martyrs' Brigades and Hamas.
The death of the Israeli woman, said to be in her 20s, on the Netiv Haasara farm marked the first fatal rocket strike in Israel since February.
Others hit another farm, an army base and a Jewish settlement in Gaza, Israeli media said.
Soon after the barrage, Palestinian police, reportedly acting on orders to stop further rocket fire, clashed with Hamas members in northern Gaza.
Five militants were wounded when police fired at their car, Hamas said.
Thursday's fatal rocket attack was the first in Israel since February
The Palestinian Authority says large numbers of Hamas activists then poured into the area, attacking a security force post and setting fire to two jeeps.
"We will not keep silent," Mushir al-Masri, a Hamas spokesman, told Reuters, calling the police action "unacceptable".
The BBC's Alan Johnston in Gaza says all this violence is only serving to escalate tensions just a month ahead of Israel's planned withdrawal from Gaza.
The Israelis say that if they come under attack during the pullout, they will retaliate with huge force.