The Israeli foreign ministry blasted what it said were "false claims" made by UNRWA.
"During the transfer of humanitarian aid into Gaza yesterday, via Kerem Shalom crossing, Hamas deliberately bombed the crossing, resulting in the death of two civilians, and over 10 injured, including an IDF soldier.
"Today, yet again, Hamas' barrage of mortars halted the transfer of humanitarian aid into Gaza.
Hamas' action should be condemned by all those who care about the Palestinians in Gaza.
UNRWA's claim that Israel is preventing humanitarian aid from reaching Gaza is a cynical misrepresentation and simply a lie," the ministry said.
"This is not the first time UNRWA has chosen to twist the facts and misrepresent events, for the sole purpose of blaming Israel. However, yesterday's statement is reaching a new low.
"Israel will continue its efforts to coordinate the transfer of humanitarian aid into Gaza, taking into account security considerations.
"We expect UNRWA to alter its statement so that it reflects reality and urge it to condemn the Hamas terrorist organization, which is to blame for this situation."