Israel's military has said it has resumed combat against Hamas after a seven-day truce between them expired with no agreement to extend it.
Both sides have been telling their forces to be ready to resume the conflict.
Fighting had been paused between the two sides since last week to allow hostages and prisoners to be freed, and for aid to get into Gaza.
The Israeli military accused Hamas of violating the seven-day truce.
A spokesperson for the Israel Defence Forces said: "Hamas violated the operational pause and in addition fired toward Israeli territory."
The ceasefire was due to expire at 7am local time (5am Irish time) on Friday - with the IDF claiming it was "ready" and willing to continue military operations.
A total of 79 Israeli hostages have been released by Hamas over seven consecutive days, with hundreds of Palestinians freed from prisons in exchange.
International mediators - including diplomats from Qatar, Egypt and the US - had been working to extend the temporary truce.
US Secretary of State Antony Blinken has been visiting the region and meeting officials on all sides to shore up support for a longer-term pause.
Reports have suggested Israel is looking to expand its military operation southward, but experts have said this phase may look different to its attacks in the north.
This is because southern Gaza, to which more than one million Palestinians have fled following Israeli orders, is now very densely populated.
It comes as four people were killed after a shooting at a bus stop in Jerusalem on Thursday.
It is reported that the fourth person was an "armed civilian" who attempted to apprehend the two attackers - but Israeli forces mistook him as hostile and seriously wounded him.
Two shooters were also killed as Israeli forces responded. Hamas has claimed responsibility for the attack.
'Irish donations saving lives'
NGO Trócaire has said Irish donations are saving lives in Gaza as it launches its Christmas appeal, which this year is focusing on 'Children in Conflict'.
The organisation has said it wants to highlight the fact that over 450 million children in the world - one out of every six - are living in a conflict zone.
Trócaire CEO Caoimhe de Barra has said the unacceptable death toll in Gaza continues to rise.
"The situation is posing huge challenges for Trócaire's partners but that they are making a difference thanks to the support of the Irish public," she said.
"Trócaire’s partner organisation, Medical Aid for Palestinians, is working against the odds in Gaza to ensure that those injured, many of them children, receive urgent medical care to give them the best chance of survival.
"Another partner, Caritas Jerusalem, has seen their medical centre and clinic in Gaza City damaged in the bombardment but staff are continuing to strive to provide whatever medical support they can.
"This life-saving work has been made possible by the generosity of people here at home."
Organisations 'unable to operate'
Ms de Barra said a pause in the conflict is not enough.
"A permanent ceasefire needs to be brokered to bring an end to the hostilities that have seen thousands of Palestinian and Israeli civilian lives lost, the majority of them women and children," she said.
"Many of Trócaire’s local partner organisations in the Gaza Strip have been unable to operate in recent weeks, and they have suffered their own horrendous ordeals through displacement and loss of friends and families.
"When they are able to do so, they must be allowed to return to delivering life-saving medical care, psychosocial support and legal assistance to the people of Gaza," she added.
Ms de Barra said while Gaza is "quite rightly in the headlines", there are also children suffering in places like Ukraine, Ethiopia and Sudan.
Before the escalation of violence last month, more than 80% of the population of the Gaza Strip were dependent on some form of humanitarian assistance.
Today, 1.7 million of the enclave's 2.2 million residents are internally displaced in an area that is half the size of County Louth.