Blasts have been reported in Gaza after Israel's prime minister Benjamin Netanyahu ordered his military to carry out "powerful" air strikes.
Witnesses said they saw explosions and heard tank fire in Gaza City and Deir al Balah.
An Associated Press reporter in Deir al Balah heard tanks firing from an area controlled by the Israeli army, and, in Gaza City, two health officials reported strikes, including near the Shifa hospital.
At least two people were killed, and four others wounded, by a strike on a neighbourhood south of Gaza City, according to Gaza's Civil Defence.
The announcement of strikes came shortly after Israel said that Hamas had opened fire on its forces in southern Gaza on Tuesday.
Hamas has denied involvement in the attack in the city of Rafah. The militant Palestinian group also said in a statement that it remained committed to the US-backed ceasefire deal.
Mr Netanyahu had also accused Hamas of violating the three-week-old ceasefire in the territory by handing over remains that were of an Israeli hostage who was already recovered.
A statement from the prime minister's office said: "Following the security consultations, Prime Minister Netanyahu instructed the military echelon to carry out powerful strikes in the Gaza Strip immediately."
US Vice President JD Vance said the ceasefire, which began on 10 October, was holding, telling reporters: "That doesn't mean there aren't going to be little skirmishes here and there.
"We know that Hamas or somebody else within Gaza attacked an (Israeli military) soldier. We expect the Israelis are going to respond, but I think the president's peace is going to hold despite that."
Hamas on Tuesday said that it would postpone the planned handover of a body of a hostage it had recovered, claiming violations of the ceasefire by Israel.
In a sign of the fragility of the ceasefire, Israeli troops were shot at in Rafah, and returned fire, according to an Israeli military official.
An Israeli military official told Sky's Middle East correspondent Adam Parsons that Hamas have "shown their true face".
The official told him: "Hamas violated the ceasefire once again, carrying out an attack against IDF forces east to the yellow line, an area under Israeli control.
"This is yet another blatant violation of the ceasefire. This comes after Hamas has also shown their true face and the fact that are pretending to not know where the remaining hostages are."
Hamas said on the Telegram messaging app that any Israeli escalation of attacks in Gaza would hinder search and recovery operations, and delay the return of the bodies of Israeli soldiers.
There are thought to be 13 bodies of hostages still in Gaza.
Read more:
Red Cross and Egyptian teams allowed into Gaza
Israel backing armed groups despite Gaza ceasefire
Speaking to Sky News, Israeli government spokesman David Mencer said: "The first line of this agreement is that all of our hostages should have been returned on the first day of this agreement.
"They were supposed to give back all of our hostages, and there was supposed to be a ceasefire. There are still 13 of our murdered hostages (in Gaza).
"And secondly, Hamas are firing on our troops. That is not a ceasefire."
'This is not about ceasing fire'
Francesca Albanese, the United Nations special rapporteur on Palestine, claimed on Sky News that there is an "ongoing genocide" in Gaza, an assertion Israel has always strongly denied, when asked about today's events.
Ms Albanese said: "There is a genocide ongoing. You want me to comment on the fact there is a ceasefire.
"I'm even uncomfortable with the term 'ceasefire', because the people in Gaza have been starved, been bombed, been left without homes. This is not about ceasing fire, it's about ceasing genocide. Israel has no right to be in the Gaza Strip, in the West Bank and in East Jerusalem.
"If Israel comes to your studio and tells you 'they have attacked a soldier in Gaza'. What was the Israeli soldier doing in Gaza in the first place?"
After the ceasefire took effect, all 20 living hostages were freed in exchange for almost 2,000 Palestinian prisoners, but the remains of the dead have been slow to be repatriated.
Hamas has said there are problems finding them due to a lack of equipment to sift through the devastation and rubble in Gaza.
The search for hostage bodies had been stepped up over the past few days after the arrival of heavy machinery from Egypt.
Bulldozers were working in Khan Younis, and further north in Nuseirat, with Hamas fighters deployed around them.
Some bodies are believed to be in Hamas' network of tunnels below Gaza.
(c) Sky News 2025: Blasts reported after Benjamin Netanyahu orders Israeli military to carry out 'powerful
'Nervous' British tourists in Jamaica tell of Hurricane Melissa ordeal
At least 64 killed as Rio police target drug gang in deadliest-ever raid ahead of COP30
Valencia floods: Anger and despair remains one year on from deadly disaster
Eleven people killed after tourist plane crashes in Kenya
The three factors keeping the Gaza ceasefire in place - for now
Slashing foreign aid will lead to unrest, crises and threaten UK security, MPs warn government
Army soldiers fled key Sudanese city - leaving 200,000 civilians trapped
More than a dozen killed as US attacks alleged drug boats in Pacific 'on Donald Trump's orders'
