Israel has lodged a complaint with Switzerland over a Swiss-Iranian natural gas purchase agreement.
The deal was signed in the Iranian capital Tehran earlier this week in the presence of the Swiss foreign minister, Micheline Calmy-Rey.
The United States has also criticised the gas deal.
Israel's foreign ministry said in a statement that it had summoned Swiss ambassador Walter Haffner to deplore Calmy-Rey's trip to Iran, calling it "an act that is unfriendly to Israel". Iran has questioned the Holocaust and has in the past called for Israel to be "wiped off the map".
Given the recent United Nations Security Council sanctions against Iran over its alleged nuclear programme, "now is not the proper time to pursue economic deals" with Tehran, the statement added.
Calmy-Rey has said that the natural gas accord breaches neither UN nor US sanctions.
Iran has denied that its atomic programme is for military ends.
During her visit, Calmy-Rey called on Tehran to cooperate with the International Atomic Energy Agency to resolve the long-standing dispute.
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