By Nidal al-Mughrabi, ‌Menna AlaaElDin and Dawoud Abu Alkas

CAIRO/GAZA CITY, Dec 14 (Reuters) - Israel's assassination of a senior Hamas commander threatens the viability of the Gaza ceasefire, ‍the chief ‌negotiator of the militant group said on Sunday, calling on U.S. President Donald Trump to demand Israel comply with the terms of the truce.

Thousands of ⁠Hamas supporters rallied in central Gaza City at a funeral for senior ‌commander Raed Saed and three associates killed alongside him on Saturday.

The mourners chanted "Martyrs are dear to God" and carried the bodies in coffins draped in green Hamas flags, in one of the group's biggest displays of its presence since a U.S.-backed ceasefire deal came into effect in Gaza in October.

In a televised address, Hamas chief negotiator Khalil al-Hayya, who lives ⁠in exile, confirmed the killing of Saed, the highest-profile assassination of a senior Hamas figure since the truce.

"The continued Israeli violations of the ceasefire agreement... and latest assassinations that targeted Saed and ​others threaten the viability of the agreement," Hayya said.

"We call on mediators, and especially the main ‌guarantor, the U.S. administration and President Donald Trump, to work on ⁠obliging Israel to respect the ceasefire and commit to it."

The Hamas armed wing said later on Sunday it has chosen a replacement for Saed, who it said had been in charge of "military manufacturing." His assassination would not deter the group from pursuing the "path of Jihad", it said.

ISRAELI FORCES HOLD ​HALF OF GAZA

Hamas sources have described Saed as the second-in-command of the group's armed wing, after Izzeldeen Al-Hadad. Israel says Saed was one of the key architects of the October 7, 2023 attack on Israel that triggered the war.

Hamas has not identified an overall chief since Israel killed the group's head, Yehya Al-Sinwar, in 2024. Instead, the group has since been led by a five-man high leadership council, of which Hayya is a member.

Since the ceasefire, Israeli ​forces remain in ‍control of the depopulated eastern half of Gaza, ​while the militant group has reasserted its control over the western half, where nearly all of the enclave's more than 2 million people live in the ruins.

The warring sides have yet to agree on next steps. Israel demands Hamas disarm and be barred from any future administration of Gaza. Hamas says it will not give up its arms and wants Israeli forces to withdraw fully.

The agreement calls for a U.N.-authorised International Stabilization Force to help keep peace. Hayya, the Hamas negotiator, said the force should be restricted to Gaza's border, outside the territory.

The U.S. Central Command, which oversees U.S. military forces in the Middle East, will ⁠host a conference in Doha on December 16 with partner nations to plan the International Stabilization Force for Gaza, U.S. officials told Reuters.

In the Central Gaza Strip, gunmen shot dead Ahmed Zamzam, a senior officer in a Hamas-run ​internal security service tasked with fighting collaboration with Israel. The Gaza Interior Ministry described the attackers as "collaborators acting upon Israeli orders" and said one suspect was detained.

Ghassan Duhine, the leader of an anti-Hamas group, the Popular Forces, based in the Israeli-occupied sector of Gaza, said his group had killed Zamzam in "a fair revenge".

Hamas brands Duhine's group and others that operate in areas Israel still occupies as collaborators. The groups ‌deny this and blame Hamas for bringing about Gaza's destruction.

Reuters could not independently verify the circumstances of the attack on Zamzam. The Israeli military did not comment.

(Reporting by Menna Alaa El-Din, Muhammad Al Gebaly, and Nidal al-Mughrabi in Cairo and Dawood Abu Abu Alkas in Gaza; Editing by Sharon Singleton and Peter Graff)