Firemen tackle a blaze caused by an Israeli rocket
Israel is tightening security ahead of demonstrations called by Palestinian militant group Hamas in protest at Israel's bombardment of the Gaza Strip.
Hamas leaders have urged Palestinians to observe a "day of wrath", after seven days of violence in Gaza.
Early on Friday, Israel bombed more targets in Gaza, including a mosque, a day after a senior Hamas leader and his family were killed in an air strike.
Palestinian militants have also fired more rockets into Israel, Israel says.
More than 400 people have died in the Israeli bombardment since it began last Saturday. The UN says at least 100 of them were civilians.
Four Israelis have been killed by rockets fired into Israel from Gaza, which have hit towns up to 25 miles (40km) from the narrow coastal strip.
Both sides have ignored international calls for a ceasefire.
Israel says its air campaign, launched in a bid to prevent militant rocket attacks from Hamas-controlled Gaza, has been going according to plan.
ROCKET ATTACKS FROM GAZA
Since the start of Israel's operations in Gaza, Israeli sources say Palestinian militants have fired the following:
27 December 2008: 61 rockets, 33 mortar shells
28 December: 14 rockets, 16 mortar shells
29 December: 57 rockets, 15 mortar shells
30 December: 42 rockets, 6 mortar shells
31 December: 43 rockets, 25 mortar shells
Source: Intelligence and Terrorism Information Center, Israel
However, BBC Middle East Editor Jeremy Bowen says a week of bombardment has not been able stop the rocket fire, and Israel now has to decide whether to send in ground troops.
Air raids have so far struck sites linked to Hamas, including smuggling tunnels under the border to Egypt, government buildings, security compounds, and homes of members of the organisation.
Israel said it attacked some 20 targets in Gaza overnight and in the early hours of Friday. It described the mosque it bombed in Jabaliya as a "terror hub" and said it was used to store weapons.
BBC staff in Gaza say at least 10 houses belonging to Hamas members were also hit, as well as a poultry farm and industrial workshop. Medical sources say two people were killed in Jabaliya.
In response to Hamas' call for protests, Israeli police have been stationed throughout East Jerusalem.
Movement for Palestinians in the West Bank has been severely restricted.
Protests have been held across the world. More than 2,000 Australian Muslims gathered in a Sydney park for Friday prayers using a symbolic coffin. Up to 5,000 gathered in the Indonesian capital Jakarta.
Israel says it has completed preparations for a possible ground offensive, and large numbers of troops and tanks are massed on the Gaza border.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.