The United States and Israel announced early on Saturday they had launched strikes against targets in Iran, sharply escalating tensions in the Middle East and prompting swift reactions from allies, including Canada and European powers.

The White House said the strikes were aimed at preventing Iran from advancing its nuclear aspirations.

In an eight-minute televised address, US President Donald Trump described the operation as an effort that could lead to regime change, urging members of Iran's Islamic Revolutionary Guard Corps to "lay down your weapons" or "face certain death".

Tehran rejected Washington's characterization and Iran's Foreign Minister Abbas Araghchi described Trump's push to topple the Islamic government as "mission impossible".

In an interview with NBC News from Tehran, Araghchi said Iran had been "acting in good faith" in negotiating an agreement on its nuclear program when the US and Israel launched their attacks.

"This is a war of choice by the United States," he said. "We made it clear for the American team that we are prepared to do everything in order to prove that our nuclear program is peaceful and would remain peaceful forever."

In a joint statement issued from Mumbai, Canada's Prime Minister Mark Carney and Foreign Minister Anita Anand said Ottawa was closely following what they called "Iran-related hostilities" and urged Canadians in Iran to shelter in place.

European powers struck a more cautious tone. The governments of France, Germany and the United Kingdom — known as the E3 — said they did not participate in the strikes and urged Tehran to end its nuclear program and seek "a negotiated solution".

In a joint statement, they called for renewed talks and said "ultimately, the Iranian people must be allowed to determine their future".

In a joint statement, European Commission President Ursula von der Leyen and European Council President Antonio Costa said the developments were "greatly concerning" and reaffirmed their "steadfast commitment to safeguarding regional security and stability".

"Ensuring nuclear safety and preventing any actions that could further escalate tensions or undermine the global non-proliferation regime is of critical importance," they said.

They called on "all parties to exercise maximum restraint, to protect civilians, and to fully respect international law", and added that the European Union would take "all necessary steps" to ensure EU citizens in the region could count on its full support.

Meanwhile, regional media reported a growing number of civilian casualties. The Tasnim news agency said the death toll from a strike on an elementary school for girls in Minab, in Hormozgan province, had risen to 85. The figures could not be independently verified.

Agencies contributed to this story