Amnesty International on Sunday called on armed Palestinian groups and Israeli forces to immediately end "unlawful" violence in Hamas-controlled Gaza.
"Such disproportionate use of force by Israel is unlawful and risks igniting further violence in the whole region," the London-based human rights group said in a statement.
"The escalation of violence comes at a time when the civilian population already faces a daily struggle for survival due to the Israeli blockade which has prevented even food and medicines from entering Gaza.
"Hamas and other Palestinian armed groups, for their part, share responsibility for the escalation. Their continuous rocket attacks on towns and villages in southern Israel are unlawful and can never be justified.
"The international community must intervene without delay to ensure that civilians caught up in the violence are protected and that the blockade on Gaza is lifted."
More than 280 people have died in less than 48 hours in raids on Gaza by Israel, with dozens of tanks and personnel carriers poised at several points near the border after Israel warned it could launch a ground offensive in addition to its massive air bombardment.