Israel is “committing barbaric massacres against unarmed civilians”, Haniyeh said in an address broadcast on Wednesday.
“Its villainy will not save them from resounding defeat,” he promised.
Israel launched an assault on Gaza on October 7 after Hamas carried out a devastating attack on southern Israel, killing at least 1,400 people, mostly civilians, according to Israeli officials.
At least 8,800 people have been killed in the continuing Israeli bombardment of Gaza, including 3,650 children, according to Palestinian authorities.
Haniyeh stated Hamas had warned Israel’s “fascist government” about its “contentious policies” before its attack, pointing to the expansion of settlements in the West Bank and attacks on Islamic holy sites, such as the Al-Aqsa Mosque.
The Hamas leader added regional unrest would continue until “Palestinians obtain their “legitimate rights to freedom, independence and return”.
The remarks came after Israel attacked the Jabalia refugee camp in north Gaza for the second straight day, killing dozens, according to Palestinian officials.
Haniyeh also stressed the bloodshed must stop and called on the world to continue rallying in defence of the Palestinian cause to pressure policymakers.
He accused Israel and its ally the United States of blocking mediation efforts.
On Friday, the US and Israel were among only 14 out of 193 UN member countries to vote “no” on the general assembly resolution calling for an immediate humanitarian truce. However, 120 countries voted “yes” to the resolution, while 45 abstained.
Israeli Prime Minister Benjamin Netanyahu has repeatedly dismissed calls for a ceasefire, stating it would be tantamount to “surrendering” to Hamas. The main Palestinian armed groups fighting in Gaza, including Hamas and the Palestinian Islamic Jihad, have not called for a ceasefire.