Iran's consulate in the Syrian capital Damascus was flattened on Monday in what Syrian and Iranian media described as an Israeli air strike.
A Lebanese security source, speaking to Reuters, said one of the dead was Mohammad Reza Zahedi, a senior commander in Iran's Revolutionary Guards Corps (IRGC). Iranian state television said several Iranian diplomats had been killed.
Israel, which has repeatedly hit Iranian targets during the six-month war in Gaza, declined to comment on the incident, following its usual practice.
An Israeli military spokesperson said: "We do not comment on reports in the foreign media."
Iran's Tasnim news agency said five people were killed in the Israeli strike. Syria's SANA state news agency reported an unspecified number of deaths and injuries.
Since the Palestinian group Hamas' attack on Israel on October 7, Israel has ramped up airstrikes in Syria against Lebanon's Hezbollah militia and Iran's Guards, both of which support the government of President Bashar Al Assad.
Iran could be producing enriched uranium in a few months, the head of the UN nuclear watchdog Rafael Grossi was quoted as saying on Sunday, raising doubts about how effective US strikes to destroy Tehran's nuclear programme have been.
The Jerusalem District Court has cancelled this week's hearings in Prime Minister Benjamin Netanyahu's long-running corruption trial, accepting a request the Israeli leader made citing classified diplomatic and security grounds.
The Israeli military ordered Palestinians to evacuate areas in northern Gaza on Sunday before intensified fighting against Hamas, as US President Donald Trump called for an end to the war amid renewed efforts to broker a ceasefire.
Russia used hundreds of drones, cruise and ballistic missiles to attack western, southern and central Ukraine overnight, damaging homes and infrastructure and injuring at least six people, local authorities said on Sunday.
At least seven Palestinians were killed and several others injured early Sunday in a series of Israeli airstrikes targeting Gaza City and Khan Younis in the southern Gaza Strip, Palestinian News & Information Agency (WAFA) reported.