A seven-hour unilateral “humanitarian window,” which was announced by Israel on Sunday evening and took effect in Gaza from 10 a.m. local time (3 a.m. EDT) Monday was almost immediately broken by an air strike on the al-Shati refugee camp in northwestern Gaza, Agence France-Presse reported.

A Gaza Health Ministry spokesperson told Al Jazeera that at least 30 people, including women and children, were injured in Israeli shelling on a residential building in the camp. And, according to other media reports, Israeli air strikes near Gaza City also killed Daniel Mansour, a commander of the Islamic Jihad group -- a close ally of Hamas -- just hours before the latest cease-fire was to begin. One child too was killed in the latest air strike on the refugee camp, AFP reported, citing doctors.

Israel had declared on Sunday that it would hold its fire in the Gaza Strip for seven hours following widespread international condemnation, including from the U.S. and the United Nations, over its attack on another U.N.-run school -- the third one since the operation began on July 8 -- on Sunday. The attack on the school in Rafah, which was reportedly sheltering thousands of displaced Palestinians, killed 10 people and injured 30 others.

Since then, Israel has reportedly been drawing down its ground operations in the Gaza Strip, although it has continued aerial attacks and shelling in many parts of Gaza, including in Rafah.

Hamas had earlier expressed reservations over the cease-fire declared by Israel and urged Palestinians living in Gaza to “take extreme caution.”

"Israel’s so-called humanitarian ceasefire is unilateral and it comes in a time when the Zionist enemy wants to distract the world from the massacres they have committed against our people in Gaza," Hamas spokesperson Sami Abu Zuhri reportedly told Al Aqsa television.

Over 1,800 Palestinians have been killed so far and over 9,000 have been injured in the four-week old Israeli operation. Sixty-seven people, including 64 soldiers, have also been killed on the Israeli side, according to Al Jazeera reports. 

UNICEF, on Monday, stated that the number of children killed in the ongoing operation, which currently stands at 392, has surpassed that of the 2008-2009 Israeli operation in Gaza, according to an Al Jazeera report.