The truce began at 7am (3pm AEDT) on Friday, involving a comprehensive ceasefire in north and south Gaza, the release of 13 Israeli women and child hostages by the militants later in the day and aid to flow into the besieged enclave.
A number of Palestinian prisoners held in Israeli prisons were to be freed in exchange.
A Reuters correspondent near the northern part of Gaza heard no Israeli air force activity overhead, and saw no tell-tale contrails typically left by Palestinian rocket launches.
Lebanon's Al-Mayadeen TV reported that since the start of the truce, no sounds of bombing were heard in Gaza.
Sirens sounded in two Israeli villages outside the southern Gaza Strip, warning of possible incoming Palestinian rockets.
There was no immediate confirmation of any launches, however.
Fighting in Gaza became even more intense up to when the ceasefire came into effect. (AP PHOTO)
Fighting had raged on in the hours before the truce, with officials inside the Hamas-ruled enclave saying a hospital in Gaza City was among the targets bombed.
Both sides also signalled fighting would resume after the pause.
The Indonesian hospital was reeling under relentless bombing, operating without light and filled with bedridden old people and children too weak to be moved, Gaza health officials said.
Al-Jazeera quoted Mounir El Barsh, the Gaza health ministry director, as saying a patient, a wounded woman, was killed and three others injured.
Additional aid would start flowing into Gaza and the first hostages, including elderly women, would be freed at 4pm (1am AEDT on Saturday), with the total number rising to 50 over the four days, Qatar's foreign ministry spokesman Majed Al-Ansari said in Doha.
Hamas-affiliated Shehab news agency reported that fuel trucks were entering the Rafah crossing once the truce was under way.
Egypt has said 130,000 litres of diesel and four trucks of gas will be delivered daily to Gaza when the truce starts, and 200 trucks of aid would enter Gaza daily.
Israel has received an initial list of hostages to be freed, the prime minister's office says. (AP PHOTO)
Palestinians were expected to be released from Israeli jails, the Qatari spokesperson told reporters.
"We all hope that this truce will lead to a chance to start a wider work to achieve a permanent truce."
Hamas confirmed on its Telegram channel that all hostilities from its forces would cease.
But Abu Ubaida, spokesman for Hamas's armed wing, later referred to "this temporary truce" in a video that called for an "escalation of the confrontation with (Israel) on all resistance fronts", including the Israeli-occupied West Bank where violence has surged since the Gaza war erupted almost seven weeks ago.
Israel's military said its troops would stay behind a ceasefire line inside Gaza.
"These will be complicated days and nothing is certain," Israeli military spokesperson Daniel Hagari said.
Israel had received an initial list of hostages to be freed and was in touch with families, the prime minister's office said.
Egypt says trucks carrying diesel and gas will be delivered daily to Gaza when the truce starts. (EPA PHOTO)
In a social media post, an Israeli military spokesman warned Palestinians: "The war is not over yet. The humanitarian pause is temporary. The northern Gaza Strip is a dangerous war zone and it is forbidden to move north. For your safety, you must remain in the humanitarian zone in the south."
Israel launched its devastating invasion of Gaza after gunmen from Hamas burst across the border fence on October 7, killing 1200 people and seizing about 240 hostages, according to Israeli tallies.
Since then, Israel has rained bombs on the tiny enclave, killing some 14,000 Gazans, about 40 per cent of them children, according to Palestinian health authorities.
"People are exhausted and are losing hope in humanity," UN Palestinian refugee agency UNRWA's Commissioner-General Philippe Lazzarini said after a visit to Gaza.
"They need respite, they deserve to sleep without being anxious about whether they will make it through the night. This is the bare minimum anyone should be able to have."
Before the ceasefire, fighting became even more intense on Thursday, with Israeli jets hitting more than 300 targets and troops engaged in heavy fighting around Jabalia refugee camp north of Gaza City.
