Palestinian officials say 10 people died in the latest attacks, taking the death toll to over 360 since Saturday. Four Israelis have died in rocket fire.
Israeli Interior Minister Meir Sheetrit rejected any ceasefire until the threat of rockets was removed completely.
A UN human rights monitor accused Israel of "shocking atrocities".
Richard Falk - the special rapporteur for human rights in the Palestinian territories - said the international community must put more pressure on Israel to end its attacks on Gaza.
"Israel is committing a shocking series of atrocities by using modern weaponry against a defenceless population - attacking a population that has been enduring a severe blockade for many months," Mr Falk said in a BBC interview.
The UN says at least 62 of the Palestinians killed so far have been women and children, and it is calling for an investigation into attacks which causing heavy civilian casualties.
Israeli jets attacked targets linked to the Hamas movement, which controls the Gaza Strip, for a fourth day, hitting a number of government buildings and security installations.