Iran blamed Israel on Tuesday for the killing of a Hamas commander in Dubai last month.
Israel's government has declined official comment on the Jan. 20 death of Mahmoud al-Mabhouh, which the Palestinian Islamist group Hamas on Friday announced as an assassination.
But Israeli security sources linked him to rockets and other arms that reach Gaza from Iran.
"This is another indication of the existence of state terrorism by the Zionist regime (Israel)," Iranian foreign ministry spokesman Ramin Mehmanparast told a news conference.
"This shows the violation of other countries' sovereignty by this regime," he added.
Police in the United Arab Emirates said they suspected a foreign "criminal gang" of killing Mabhouh in his hotel room, while not ruling out involvement of Israel's Mossad spy agency.
Israel says Iran bankrolls attempts to ship weapons to Gaza by sea or land. Iran, which does not recognize the Jewish state, says its support for Hamas is diplomatic only.
Mehmanparast said, "The silence of international forums and some other countries toward committing such crimes is really surprising ... Islamic countries must be more vigilant regarding the danger of this illegitimate regime and make due plans."
The Mossad is believed to have stepped up missions against Hamas, Lebanon's Hezbollah militia and Iran's nuclear project. Among killings attributed to the agency were that of Hezbollah commander Imad Moughniyeh in Damascus two years ago.
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