Here is a roundup of key reactions:

- 'Cannot have nuclear bomb': United States -

US President Donald Trump, told Fox News he was aware Israel was going to conduct strikes on Iran before they happened and said: "Iran cannot have a nuclear bomb and we are hoping to get back to the negotiating table. We will see."

Fox News also reported that "Trump noted the US is ready to defend itself and Israel if Iran retaliates."

- 'Maximum restraint': UN -

UN chief Antonio Guterres asked "both sides to show maximum restraint, avoiding at all costs a descent into deeper conflict, a situation that the region can hardly afford," according to a spokesperson.

Guterres was "particularly concerned" by Israel's strikes on nuclear installations amid the ongoing US-Iran negotiations.

- 'Unacceptable' and 'unprovoked': Russia -

"Russia is concerned and condemns the sharp escalation of tensions," spokesman Dmitry Peskov told state news agencies, calling the strikes "unacceptable" and "unprovoked", while the Russian embassy in Tel Aviv urged Russians in Israel to leave the country.

- 'Deeply worried': China -

"The Chinese side... is deeply worried about the severe consequences that such actions might bring," foreign ministry spokesman Lin Jian said, calling "on relevant parties to take actions that promote regional peace and stability and to avoid further escalation of tensions".

- 'Diplomacy best path forward': EU -

"The situation in the Middle East is dangerous. I urge all parties to exercise restraint and prevent further escalation. Diplomacy remains the best path forward, and I stand ready to support any diplomatic efforts toward de-escalation," said EU foreign policy chief Kaja Kallas.

- Avoid 'further escalation': Germany -

Germany, which for years expressed concerns about Iran's "advanced nuclear weapons programme", said it was "ready to use all diplomatic means at our disposal to influence the parties to the conflict. The goal must remain that Iran does not develop nuclear weapons".

- 'Dangerous escalation': Hamas -

"This aggression constitutes a dangerous escalation that threatens to destabilise the region," said the Iran-backed, Palestinian militant group, whose October 2023 attack on Israel sparked the Gaza war.

- 'Threat to international peace': Iraq -

Iraq strongly condemned the attacks, saying: "This act represents a blatant violation of the fundamental principles of international law and the Charter of the United Nations, and constitutes a serious threat to international peace and security."

- No 'battleground': Jordan -

"Jordan has not and will not allow any violation of its airspace, reaffirming that the Kingdom will not be a battleground for any conflict," a government spokesperson told AFP after Jordan closed its airspace.

- 'Dangerous approach': Oman -

Nuclear talks mediator Oman said "calls on the international community to adopt a clear and firm position to put an end to this dangerous approach, which threatens to rule out diplomatic solutions and jeopardise the security and stability of the region".

- 'Strong condemnation': Qatar -

Gaza mediator Qatar expressed "its strong condemnation and denunciation of the Israeli attack," the Gulf state's foreign ministry said, adding that the "dangerous escalation threatens security and stability of the region and hinders efforts to de-escalate and reach diplomatic solutions".

- 'Aggressive actions': Turkey -

"Israel must put an immediate end to its aggressive actions that could lead to further conflicts," said Turkey's foreign ministry.

- 'Reduce tensions urgently': UK -

British Prime Minister Keir Starmer said: "The reports of these strikes are concerning and we urge all parties to step back and reduce tensions urgently. Escalation serves no one in the region."

- 'Legitimate right to defend itself': Yemen's Huthis -

Tehran-backed Huthi rebels said they backed "Iran's full and legitimate right to... develop its nuclear programme" and that "we strongly condemn the brutal Israeli aggression against the Islamic Republic of Iran and affirm its full and legitimate right to respond by all possible means".

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