Palestinian terrorist factions in the Gaza Strip signaled readiness for an informal, and apparently unilateral cease-fire with Israel on Monday night, but said it depends on "Israeli aggression," Palestinian news agencies reported. The report comes at the end of a day that saw over 20 rockets fired into Israel, injuring four people.Hamas called the meeting of the various factions in order to avoid further Palestinian casualties, Bethlehem-based Ma'an news agency reported, citing a DFLP leader. Six Palestinians have been killed in Israeli strikes since the weekend, four of whom were civilians. A Hamas statement from the meeting said that its activities "depend on the continuation of the Israeli aggression."Soon after the meeting, however, Gazans fired three additional rockets at Sderot. The rockets exploded in open areas, causing no damages or injuries.Palestinian terrorists in the Gaza Strip fired some 20 rockets and mortars into southern Israel since midnight Sunday, injuring four people, with 43 others suffering from shock.The attacks mark the third straight day of escalations. Over the weekend, terrorists fired some 100 rockets into the South, leaving three people injured in Sderot.The Iron Dome missile-defense system intercepted two rockets near Ashkelon and later in the day, intercepted two Grad rockets fired toward Ofakim.One Grad rocket hit an abandoned residential home in Netivot earlier Monday, causing significant damage to the building. Another, later in the day, caused damage in Netivot's industrial area.The Israeli Air Force struck three targets in the Gaza Strip overnight Sunday. The warplanes targeted a tunnel used for terrorist purposes and a weapons storage facility in the northern Gaza Strip, and a rocket-launching site in the south of the Strip, the IDF Spokesman's Office said in a statement. The airstrikes, the IDF said, were in response to the rocket and mortar fire into Israel.No injuries were reported from the air strikes.Ben Hartman, Yaakov Lappin and Reuters contributed to this report.