Philippe Lazzarini said on social media platform X on Sunday that “the dire humanitarian condition in war-battered Gaza is a man-made disaster”.
Famine can still be avoided through genuine political will to grant access and protection to meaningful assistance, he added.
Lazzarini said that the last time UNRWA was able to send food aid to northern Gaza was on January 23.
Aid agencies have increasingly voiced concern for ordinary Gazans caught up in Israel's military campaign.
The UN has already warned of looming famine threatening virtually everyone in Gaza, while the World Food Programme this week described "unprecedented levels of desperation". In recent days, a number of children have died of starvation in Gaza.
UNRWA has been a lifeline for millions of Palestinians since 1949, just months after the creation of Zionist entity on the occupied Palestinian land.
The agency is now facing abolition calls from Israel after the regime leveled allegations that some UNRWA staff members were involved in Palestinians’ Al-Aqsa Storm operation on October 7.
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