A rocket has been fired at Jerusalem by Hamas - the first time the holy city is thought to have been targeted by Gaza militants using such a weapon.
Israeli police said the rocket landed in an open area near Gush Ezion, a collection of Jewish settlements in the West Bank southeast of the city.
The rocket caused no damage or injuries, the Jewish state's army said.
But an attack on what Israelis call their capital marks a significant escalation by Gaza militants, both for its symbolism and its distance from the Palestinian territory.
Located about 55 miles away from the Gaza border, Jerusalem had been thought to be beyond the range of Gaza rocket squads.
The armed wing of Hamas, Al Qassam Brigades, said on Twitter: "Al Qassam Brigades launch two M75 homemade missiles towards occupied Jerusalem."
Four Palestinians have been killed in a new Israeli strike on Gaza, a Hamas health ministry spokesman said, as multiple new raids struck throughout the territory.
Among the four to die was reportedly Ahmed Abu Jalal, a field commander of Hamas's armed wing.
Twenty-nine Palestinians - including 13 militants - have now been killed in the recent violence. Three Israelis were killed by a rocket on Thursday.
The Israeli military said nearly 200 rockets fired from Gaza hit Israel on Friday - half were intercepted by its Iron Dome anti-missile system.
Earlier on Friday, there was a second rocket attack by Palestinian militants on Tel Aviv in 24 hours.
Air raid sirens went off in the centre of Israel's largest city on Friday afternoon and people were forced to scramble for cover. There were no reports of any injuries and it is thought to have landed in the sea.
"We are sending a short and simple message: There is no security for any Zionist on any single inch of Palestine and we plan more surprises," Abu Obeida, spokesman for the Hamas militant wing, said of the rockets aimed at Israel's two main cities.
It was the second day in a row that a rocket from Gaza had reached the Tel Aviv area in what Israeli networks said was the first time rockets had been fired at the city since the 1991 Gulf War, when it was hit by Iraqi Scud missiles.
On Thursday, another rocket fell in the sea and the other landed in a Tel Aviv suburb, causing no damage or casualties. Israel responded with airstrikes.
The latest rocket came as the Israeli air force continued a major bombing campaign across Gaza Strip as it targeted suspected rocket launching sites.
Senior Israeli cabinet minister Moshe Yaalon warned that Israel was considering a ground operation in order to stamp out rocket fire.
"We are preparing all the military options, including the possibility that forces will be ready to enter Gaza in the event that the firing doesn't stop," he wrote in a series of postings on his official Twitter account.
There were fresh exchanges of fire between Israel and Hamas militants on Friday despite a temporary ceasefire in place for a visit by Egypt's prime minister Hisham Kandil to Gaza.
Several sites in southern Israel have been hit by rockets fired from inside the Gaza Strip, while a Hamas source said the Israeli air force attacked a Hamas commander's house which resulted in the death of two civilians, one a child.
But Israel's military strongly denied carrying out any attack from the time Mr Kandil entered Gaza, and accused Hamas of violating the three-hour deal.
During his visit, the Egyptian PM condemned Israeli action against Gaza as "unacceptable aggression", saying his country will intensify efforts to secure a truce in the conflict.
"This tragedy cannot pass in silence and the world should take responsibility in stopping this aggression," he said at a news conference in Gaza City's Shifa hospital after seeing some victims from an airstrike.
"Egypt will not hesitate to intensify its efforts and make sacrifices to stop this aggression and achieve a lasting truce."
His visit comes as 16,000 Israeli army reservists have been called up and heavy artillery has been seen on the Gaza border, increasing the possibility of a ground attack.
Israeli ministers have reportedly approved the call-up of as many as 75,000 reservists as Prime Minister Benjamin Netanyahu held late evening talks with his inner circle.
Meanwhile, European Union foreign policy chief Baroness Ashton said Israel had the right to protect its people against Gaza rocket attacks but urged it to stick to a "proportionate" response.
She also voiced hopes that the Egyptian prime minister "will be able to calm the situation".
And Britain's Foreign Secretary William Hague urged both Israel and the Palestinians to make efforts to halt the violence.
But Mr Hague made it clear that he believes Hamas bears the greatest responsibility for the current crisis, as well as the ability to bring it most swiftly to an end.
The conflict has been intensifying over recent weeks, but flared up dramatically in the wake of the Israeli strikes against senior Hamas figures.
Mr Netanyahu has warned his country is prepared to extend its operation against Hamas, sparking fears of a repeat of the ground incursion four years ago in which hundreds died.