Any escalation of military activities will be "catastrophic" for people in the Gaza Strip, the UN high commissioner for refugees said Friday.
Hamas stormed into Israel from the Gaza Strip on October 7 and killed at least 1,400 people.
Israel says around 1,500 Hamas fighters were killed in clashes before its army regained control of the area under attack.
More than 3,700 Palestinians, mainly civilians, have been killed across the Gaza Strip in relentless Israeli bombardments in retaliation for the attacks by the Palestinian fighter group, according to the latest toll from the Hamas health ministry in Gaza.
"(I) can tell you with certainty that any further escalation or even continuation of military activities will just be catastrophic for the people of Gaza," Filippo Grandi told reporters in Japan on Friday.
While stressing that the refugee agency UNHCR has no formal mandate in the Palestinian Territories or Israel, Grandi said that he "shares the extreme worry and anguish that has been expressed by many of my colleagues including the UN secretary-general" about the conflict.
He also called the Hamas attacks in Israel on October 7 "appalling" and said that the consequences of the conflict spreading into Lebanon and elsewhere would be "incalculable".
"Lebanon is in a profound political and economic crisis itself. Lebanon hosts hundreds of thousands of refugees; Syrian refugees and Palestinian refugees," Grandi said.
"So if God forbid Lebanon were to be engulfed in this war, the humanitarian consequences will be incalculable," Grandi said.
"Let us not forget that we have other situations not resolved in the vicinity. The Syria conflict for example. Iraq remains very fragile. Egypt has hosted hundreds of thousands of refugees from Sudan, another conflict on its borders," he said.
The UN says more than one million of Gaza's 2.4 million people have been displaced and that the humanitarian situation is worsening by the day.
Italian diplomat Grandi, 66, was in Japan seeking funding for the UNHCR's activities supporting the 110 million people displaced from other places such as Afghanistan, Myanmar, Syria, and Sudan.
"Although crises are growing, funding is not growing. Up to now... almost at the end of the year, for example, the UNHCR is only funded at 42%," he said.
