A "worst-case scenario of famine" is playing out in Gaza as access to food plummets to unprecedented lows, according to the IPC global hunger authority.

A worst-case scenario of famine is unfolding in Gaza and immediate action is needed to end fighting and allow unimpeded aid access, a global hunger monitor warned on Tuesday, saying failure to act now would result in widespread death.

The announcement comes as severe acute malnutrition continues to rise across Gaza. One-fifth of children are currently affected, and up to half of those may not survive, Dr. Zaher Sahloul, co-founder and president of MedGlobal, told “NewsNation Now” on Monday.

Israel announced Sunday it would take a "tactical pause" in fighting to allow aid delivery to Gaza after countries issued a statement: war "must end now."

ABC News’ Chief Foreign Correspondent Ian Pannell reports on Gaza’s latest situation, widespread famine, on “This Week.”