Israel and Hamas entered a four-day ceasefire on Friday with the Palestinian militants set to release a first group of hostages later in the day and increased aid to flow into the besieged Gaza Strip, the first pause in a nearly seven-week-old war.

The truce began at 1pm Hong Kong time involving a comprehensive ceasefire in north and south Gaza, and was to be followed by the release of some of the more than 200 hostages taken by Hamas during the Islamists' October 7 attack inside Israel, mediators in Qatar said.

A number of Palestinian prisoners held in Israeli prisons were to be freed in exchange. Fighting raged on in the hours leading up to the truce, with officials inside the Hamas-ruled territory saying a hospital in Gaza City was among the targets bombed.

Both sides signalled the pause would be temporary before fighting resumes.

Hamas confirmed on its Telegram channel that all hostilities from its forces would cease.

But Abu Ubaida, spokesperson for Hamas' armed wing, later referred to "this temporary truce" in a video message 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, without giving details of its position.

"These will be complicated days and nothing is certain," Israeli military spokesperson Daniel Hagari said. "Control over northern Gaza is the first step of a long war, and we are preparing for the next stages," he added.

Israel launched its devastating invasion of Gaza after gunmen from Hamas burst across the border fence in October, killing 1,200 people and seizing about 240 hostages, according to Israeli tallies.

Since then, Israel has rained bombs on the territory, killing some 14,000 Gazans, around 40 percent 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 on Thursday after a visit to Gaza, referring to "unspeakable suffering" there.

"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." (Reuters)