Explosions were heard in multiple Iranian cities, including Tehran, on Monday as the Israeli air force began a new wave of strikes across the country, according to Xinhua.

Iran launched several missiles towards Israel on Sunday evening and warned the latter not to retaliate, in the first such strikes since a ceasefire was reached in April. 

The Israel Defense Forces (IDF) said in a statement that Iran fired 10 missiles towards Israel on Sunday night. The missiles triggered sirens across northern Israel. There were no immediate reports of injuries or damage. 

IDF Chief of Staff Eyal Zamir said the military "will strike the enemy with determination as soon as the order is given."

Iran's Islamic Revolution Guard Corps confirmed in a statement that it targeted Israel's Ramat David Airbase with ballistic missiles in response to its "widespread crimes" in Lebanon.

According to Iran's semi-official Fars News Agency, Chief Commander of Iran's Khatam al-Anbiya Central Headquarters Ali Abdollahi said Sunday night that if Israel expands its attacks on southern Lebanon and the Dahieh district south of Beirut, or responds to Iran's actions, it will face more "crushing and regret-inducing blows."

Iran's attacks came after Israel launched airstrikes on Beirut's southern suburbs earlier in the day, which Lebanon's Public Health Emergency Operations Center said killed at least two people and injured 20 others. The developments came despite Israel and Lebanon agreeing on Wednesday to implement a ceasefire following trilateral negotiations in Washington.

Following the latest flare-up, the IDF said it would continue to operate "across Lebanon" and intensify its operation against the Iran-backed militant group.

Trump seeks de-escalation

US President Donald Trump on Sunday urged Iran to stop launching missiles at Israel and return to negotiations. 

"What I would suggest to Iran: You've shot your missiles, that's enough," Trump told Fox News. "Get back to the table and make a deal."

Trump also claimed that Washington and Tehran had been close to reaching an agreement before Iran launched the missiles earlier in the day. 

Trump and Israeli Prime Minister Benjamin Netanyahu spoke by phone on Sunday after Iran fired missile barrages at Israel in response to airstrikes in Beirut, Israel's state-owned Kan TV news reported. Neither Netanyahu's nor Trump's office immediately commented on the call.

Before the call, Trump told Israel's Channel 12 News that he would tell Netanyahu not to strike back because he did not want US-Iran ceasefire negotiations to collapse.

Regional countries close airspace

Amidst the renewed regional tensions, Iraq announced on Sunday night the temporary closure of its airspace to all flights for 72 hours as a precautionary measure. Syria said it had closed its southern air routes for 12 hours and suspended operations at Damascus International Airport.

According to Iran's semi-official Tasnim News Agency, Iran announced on Sunday night the closure of its western airspace until further notice. An IRNA report said that Iran also suspended flights at Imam Khomeini International Airport.

(With input from Xinhua)