U.N. Secretary-General Antonio Guterres on Thursday urged an immediate cease-fire in Gaza after Israel announced the first steps of an operation to seize Gaza City.

"It is vital to reach immediately a cease-fire in Gaza," that was necessary "to avoid the death and destruction that a military operation against Gaza City would inevitably cause," Guterres said in Japan, where he is attending the Tokyo International Conference on African Development.

Israel, which has called up tens of thousands of army reservists, is pressing ahead with its plan to seize Gaza's biggest urban center despite international criticism of an operation likely to force the displacement of many more Palestinians. Israel currently holds about 75% of the Gaza Strip.

The war on Gaza was triggered by the Oct. 7 Hamas incursion, which caused around 1,200 deaths and took over 200 hostages, according to Israeli figures.

Israel's genocidal war, in comparison, has killed at least 61,000 Palestinians, according to the enclave's Health Ministry.