JERUSALEM (Reuters) - Israel swore in a new commander of its military on Wednesday as a standoff over the fragile ceasefire in Gaza increased the risk of a resumption of fighting without an agreement to bring home the rest of the hostages still held by Hamas.

Eyal Zamir, who retired after 28 years with the rank of Major General, was promoted to Lieutenant General, before formally assuming command from General Herzi Halevi, who stepped down over the security disaster of Oct. 7, 2023.

"The mission I have been given is clear, to lead the IDF to victory," he said.

Fighting in Gaza has been halted since January under a truce brokered by Qatar and Egypt and supported by the United States that has allowed the exchange of 33 Israeli hostages and 5 Thais for around 2,000 Palestinian prisoners and detainees.

A related war in southern Lebanon, which broke out after Iranian-backed Hezbollah forces launched missile strikes against Israel after the October 7 attack, has also been silenced by a separate ceasefire agreement.

But Israeli ministers and officials have warned that their forces could resume fighting if there is no agreement on bringing back the 59 hostages that remain.

Israeli troops have pulled back from some of their positions in Gaza but talks that were intended to agree the release of the hostages and the full withdrawal of Israeli forces before an end to the war have not begun.

Israel has called for an extension of the truce until after the Jewish Passover holiday in April to allow the release of the remaining hostages, while Hamas has insisted on proceeding to talks on a permanent end to the war bafore agreeing to any further releases.

Zamir's appointment comes as a series of official inquiries have begun to examine the failures that allowed thousands of Hamas-led gunmen to storm Israeli communities around the Gaza Strip, killing 1,200 people and seizing 251 hostages in one of the biggest military and security disasters in Israel's history.

Halevi led the military during the Israeli campaign in Gaza that killed more than 48,000 Palestinians and destroyed much of the enclave, leaving most of the population sheltering in tents or bombed-out buildings.

But he announced in January, soon after the Gaza ceasefire deal was agreed, that he would step down from his command, accepting responsibility for the military's patchy and uncoordinated response to the Oct. 7 attack.

Both the Israel Defence Forces and the Shin Bet security agency have acknowledged that their failures allowed the attack to take place but Prime Minister Benjamin Netanyahu has so far resisted a more general inquiry that would look at the responsibility of his government.

The new commander will also have to respond to accusations from international bodies including the United Nations that Israeli troops committed war crimes during the campaign in Gaza.

Israel rejects those charges, which it says are motivated by political hostility towards the state of Israel but it has indicted some individual reservist soldiers for severe abuse of detainees.

Israel says Hamas, which has also been accused of war crimes by United Nations bodies, committed multiple atrocities during the October 7 attack and severely abused Israeli hostages in Gaza. Hamas denies the accusations.

(Reporting by James Mackenzie)