Mr. Sunak said he had spoken to his Israeli counterpart, Mr. Netanyahu, and offered to send 'diplomatic or security support', vowing that 'terrorism will not prevail'.
UK Prime Minister, Rishi Sunak has backed Israel against Hamas.
This is as he announced that British intelligence will help Israel bring to justice terrorists who have killed at least 700 people and taken more than 100 hostages,
In an unprecedented show of support, the Prime Minister on Sunday night, pledged 'steadfast support' for Benjamin Netanyahu and indicated that MI6 would help Israel track down the Hamas killers who unleashed the bloodiest attack on the country in 50 years.
Mr. Sunak said he had spoken to his Israeli counterpart, Mr. Netanyahu, and offered to send 'diplomatic or security support', vowing that 'terrorism will not prevail'.
A UK government source said the unprecedented offer included potential assistance in identifying 'threats and targets'.
Downing Street has also issued a message of support by lighting up the building with the Israeli flag in an expression of solidarity. Mr Sunak, who tweeted a picture of the display, said: 'We stand with Israel.'
Meanwhile, the Government is working to establish the status of UK citizens in Israel after the attacks saw at least one British man serving in the country's army killed.
The Prime Minister has condemned the Palestinian militants for the 'appalling act of terror' on Israel and described the events of the past 36 hours, in which at least 700 people have been killed, as 'truly horrifying'.
In a statement delivered from Chequers on Sunday, Mr Sunak said: 'The scenes that we've seen in Israel over the past 36 hours are truly horrifying.
'I want to express my absolute solidarity for the people of Israel now is not a time for equivocation, and I'm unequivocal. Hamas, and the people who support Hamas, are fully responsible for this appalling act of terror, for the murder of civilians and for the kidnapping of innocent people, including children.'
Mr Sunak said he had spoken with the Israeli PM earlier today to offer the UK's ongoing support, adding: 'Terrorism will not prevail.'
Britain's PM said he offered Mr Netanyahu 'any support' Israel needs in a conversation with the Israeli Prime Minister this afternoon, Downing Street said.
Mr. Sunak also stressed his commitment to 'ensuring the Jewish community in the UK feels safe and secure at this time', according to a readout.
A No 10 spokesperson said: 'The Prime Minister spoke to Israeli Prime Minister Benjamin Netanyahu this afternoon, following deadly attacks by Hamas against Israel.
'He reaffirmed that the UK will stand with Israel unequivocally against these acts of terror. The Prime Minister offered Prime Minister Netanyahu any support Israel needs.
'The Prime Minister outlined the diplomatic work the UK is doing to ensure the world speaks with one voice in opposition to these appalling attacks.
Prime Minister Netanyahu thanked the Prime Minister for the UK's support.
'The Prime Minister also stressed his commitment to ensuring the Jewish community in the UK feels safe and secure at this time. The leaders agreed to stay in close contact as the situation develops.'