The EU foreign ministers echoed the call following a meeting in the French capital, Paris.
Food, urgent medical aid, fuel and humanitarian workers should be allowed in to Gaza and the injured evacuated, it said.
Diplomatic efforts to achieve a lasting peace deal should be stepped up, it added.
Earlier in the day French Foreign Minister Bernard Kouchner proposed a 48-hour truce to allow aid in to Gaza; Israel has yet to respond.
But the BBC's correspondent in Paris says the Israeli government has little time for many European governments' positions and the ministers are well aware of their relative impotence.
The US - Israel's strongest ally - has called for a long-term solution beyond any immediate ceasefire. But the White House reiterated that the onus was on Hamas to act first to end the violence.
Israeli Prime Minister Ehud Olmert said earlier that the air assault on Gaza was "the first in several stages" of operations against Hamas. Another top official said Israel was ready for "long weeks of action".
Israel has massed forces along the boundary with Gaza and has declared the area around it a "closed military zone".
Correspondents say the move could be a prelude to ground operations, but could also be intended to build pressure on Hamas.
The Israeli air strikes began less than a week after the expiry of a six-month-long ceasefire deal with Hamas.
Israel withdrew from Gaza in 2005 but has kept tight control over access in and out of Gaza and its airspace.
GAZA VIOLENCE 27-30 DECEMBER
1. Ashdod: First attack so far north, Sunday. Woman killed in second rocket attack, Tuesday 2. Ashkelon: One man killed, several injured in rocket attack, Monday 3. Sderot: rocket attacks 4. Nevitot: One man killed, several injured in rocket attack, Saturday 5. Civilian family reported killed in attack on Yabna refugee camp, Sunday 6. Israeli warplanes strike tunnels under Gaza/Egypt border, Sunday 7. Three brothers reported killed in attack on Rafah, Sunday 8. Khan Younis: Four members of Islamic Jihad and a child reported killed, Sunday. Security officer killed in air strike on Hamas police station, Tuesday 9. Deir al-Balah: Palestinians injured, houses and buildings destroyed, Sunday 10. Tel al-Hawa - Interior ministry and Islamic University badly damaged, Monday. At least three buildings in ministry compound hit, Tuesday 11. Gaza City port: naval vessels targeted, Sunday 12. Shati refugee camp: Home of Hamas leader Ismail Haniya targeted, Monday 13. Intelligence building attacked, Sunday 14. Jebaliya refugee camp: several people killed in attack on mosque, Sunday 15. Beit Hanoun - two girls killed in air strike, Tuesday 16. Israeli soldier killed at unspecified military base near Nahal Oz border crossing - five other soldiers wounded in same rocket attack, Monday night.
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