By Parisa Hafezi

DUBAI (Reuters) -Iran's top envoy accused Israel of seeking "genocide" by enforcing a siege against the Gaza Strip, Iranian state TV reported on Thursday, as he began a regional tour to discuss the conflict between Tehran's Palestinian ally Hamas and Israel.

Israel said there would be no humanitarian break to its siege of the Gaza Strip, launched after Hamas militants' devastating attacks on Israel on Saturday, until all Israelis taken hostage that day were freed.

The Red Cross pleaded for fuel to be allowed into Gaza to prevent overwhelmed hospitals from "turning into morgues".

Before leaving Tehran for Iraq, the first leg of his tour that includes Lebanon and Syria, Hossein Amirabdollahian said: "The war ... in the Gaza Strip is not just the Zionists' war against a group, it is a war against all Palestinians.

"Today, the continuation of war crimes by (Israeli Prime Minister Benjamin) Netanyahu and Zionists against the civilians in Gaza, besieging, cutting off water and electricity, and denying entry of medicine and food, has created conditions where the Zionists are seeking a genocide of all people in Gaza," he said.

Iranian President Ebrahim Raisi and Saudi Arabia’s Crown Prince Mohammed Bin Salman discussed the Israeli-Palestinian conflict in a phone call, the first contact between the two leaders since resumption of ties between Tehran and Riyadh under a China-brokered deal in March.

As part of Tehran's efforts to reach an agreement with regional countries on a position to support Palestinians, Raisi also held a phone call with Syrian President Bashar al-Assad.

Since the 1979 Islamic Revolution, Iran's clerical rulers have been most vocal backing the Palestinian cause as a pillar of the Islamic Republic.

Iran has made no secret of its backing for Hamas, funding and arming the group and another Palestinian militant organisation, Islamic Jihad.

But Iran's Supreme leader Ayatollah Ali Khamenei said on Tuesday that Tehran was not involved in the Hamas attack on Israel. However, he hailed what he called Israel's "irreparable" military and intelligence defeat.

(Additional reporting by Elwely Elwelly and Dubai newsroom, Writing by Parisa HafeziEditing by Andrew Cawthorne, Angus MacSwan and Nick Macfie)