The UK will send two Royal Navy ships and surveillance aircraft to the eastern Mediterranean in plans to "bolster security", No 10 says.
It comes after six days of violence following the surprise attack on Israel by Hamas.
The aircraft will begin patrols on Friday to "track threats to regional stability such as the transfer of weapons to terrorist groups".
Three Merlin helicopters and Royal Marines are also being dispatched.
The government is also arranging flights for British nationals stranded in Israel. The first plane was expected to leave Tel Aviv on Thursday, but as of Friday morning it had not yet left.
A Foreign Office spokesperson said the situation around departure was "fluid", and it was "currently working to ensure the flight can proceed as soon as possible".
Rishi Sunak spoke to Israel's prime minister on Thursday to reaffirm the UK's support.
His call to Benjamin Netanyahu was meant to "reaffirm the UK's steadfast support for Israel following Hamas' appalling terrorist attack", Downing Street said.
No 10 added that military assistance would be "deployed in the coming days to bolster security in the wider region" and reiterated that the UK "stands side by side with Israel in fighting terror".
Defence Secretary Grant Shapps said the vessels were not warships, but "ships that can assist with hospital facilities".
He told OceanNewsUK sending the boats was also about "deterring others from getting involved in the region" and "maligning external influence".
When asked about Israel's response to the attacks, the defence secretary said "Israel has the right to defend itself" and added that, "unlike Hamas", it was giving warning "that it's coming after Hamas terrorists" which was the right thing to do.
Mr Sunak spoke to Egyptian President Abdul Fattah al-Sisi on Thursday morning to discuss the importance of opening the Rafah crossing into Gaza to allow for humanitarian access and provide a route for British and other nationals to leave.
Speaking on Thursday, he said the UK's military and diplomatic teams across the region would support international partners to "re-establish security and ensure humanitarian aid reaches the thousands of innocent victims of this barbaric attack from Hamas terrorists".
Hamas launched an unprecedented attack on southern Israel on Saturday, killing at least 1,300 and taking around 150 hostages to Gaza.
More than 1,300 have also been killed in Gaza since Israel launched retaliatory air strikes.
