Hamas chief Yahya Sinwar said Monday the Palestinian group had the resources to sustain its fight against Israel, with support from Iran-backed regional allies, nearly a year into the Gaza war.

Sinwar, who last month replaced slain Hamas leader Ismail Haniyeh, said in a letter to the group's Yemeni allies: "We have prepared ourselves to fight a long war of attrition."

Deadly fighting raged on in the besieged Gaza Strip, where medics and rescuers said Monday that Israeli strikes — which the military has not commented on — killed at least two dozen people.