Israeli forces launched strikes in Iran and Lebanon early Monday, and Iran retaliated with missile attacks that sent sirens sounding across Israel, according to NPR. The escalation threatens to drag the Middle East back into an all-out war after weeks of a fragile truce.

Iran said it targeted two Israeli military bases in retaliation for Israeli strikes on Iranian radar sites, the outlet reported. Israel struck central and western Iran early Monday after attacking Hezbollah targets in the Lebanese capital, Beirut.

Yemen’s Houthi rebels, an Iranian ally, joined the attack, firing missiles at Israel alongside Iran, according to NPR.

The violence marks a dramatic breakdown of the relative calm that followed an Israeli-Lebanon ceasefire reached in April. That 10-day truce, which took effect April 16, had been renewed in early June, with both sides agreeing to extend it as the U.S. pursued a separate nuclear deal with Iran.

Over the weekend, the region saw escalating exchanges that foreshadowed Monday’s strikes. On June 7, Iran fired waves of missiles at Israel after an Israeli airstrike on Beirut, according to prior reporting. A day earlier, Israeli airstrikes killed nine people in Lebanon, including several Lebanese army officers, dealing a blow to the ceasefire that had been renewed just days earlier.

The renewed hostilities have drawn in multiple Iranian-aligned groups across the region, including the Houthi movement in Yemen, which began launching strikes at Israel in March. That dynamic had previously been contained by the now-faltering ceasefires.

Diplomatic efforts to de-escalate the crisis face steep new hurdles. The U.S. had been pressing for both a wider cease-fire framework and a nuclear agreement with Iran, but Monday’s cross-border attacks have gutted trust on all sides.

No casualty figures from the latest round of strikes were immediately available, and independent verification of the military claims remained limited.