Iran and Israel on Monday attacked each other's territory for the first time since a shaky ceasefire put five weeks of war on hold, sparking fears the escalation could spark a new full-scale conflict.

The attack would be the first since a fragile ceasefire took effect in early April, complicating mediation efforts for a deal to end the war.

Air raid sirens sounded in Israel on Sunday as its military worked to intercept barrages of incoming Iranian missiles for the first time since an April ceasefire took hold in the…