Open hostilities between Israel and Iran entered a fourth day on Monday with no sign of easing, stoking fears of a wider war in the oil-rich region.

Iran has told mediators Qatar and Oman that it is not open to negotiating a ceasefire while it is under Israeli attack, an official briefed on the communications told Reuters on Sunday, as the two foes launched fresh attacks and raised fears of a wider conflict.

BEIRUT — Iran and Israel traded air raids and ballistic missile barrages overnight and into the evening Sunday, with neither side showing any inclination to back down from an escalating grudge match between the two longtime enemies.