Switzerland has joined a chorus of international criticism against Israeli military action in the Gaza Strip that has killed more than 200 Palestinians.
The foreign ministry acknowledged that Israel has a right to protect itself but condemned Saturday's attacks on Gaza City as "excessive".
The ministry has called for a ceasefire from all sides and for humanitarian supplies to be allowed into the blockaded area immediately.
The Israeli military launched the attacks against Hamas targets in Gaza as a fragile truce crumbled into heavy rocket fire on Saturday. One Israeli civilian was killed after Hamas soldiers fired a rocket into a nearby Jewish town.
Television stations in the region showed pictures of panicked Palestinians scrambling to remove the wounded from destroyed buildings. Senior Hamas officials have also been killed.
"There is blood everywhere, there are wounded and martyrs in every house and in every street," Hamas leader Ismail Haniyeh told Palestinians. "We will not leave our land, we will not raise white flags and we will not kneel except before God."
The International Committee of the Red Cross also expressed deep worry over the situation as the death toll continued to climb on Sunday.
A senior Israeli military official said the barrage was the "opening step" in an operation that could last for many days.