Britain on Saturday called for a swift end to the violence in the Gaza Strip, the worst escalation in hostilities since a war last year.

"The UK stands by Israel and its right to defend itself," Foreign Secretary Liz Truss tweeted.

"We condemn terrorist groups firing at civilians and violence which has resulted in casualties on both sides."

"We call for a swift end to the violence."

At least 15 people, including a five-year-old girl, have been killed inside Gaza in the latest eruption of hostilities, according to Gaza health authorities.

Israel hit Gaza with deadly air strikes on Saturday and a Palestinian militant group retaliated with a barrage of rocket fire.

Israel said it was forced to launch a "pre-emptive" operation against Islamic Jihad, insisting the group was planning an imminent attack following days of tensions along the Gaza border.

An 11-day conflict in May 2021 between Israel and Gaza militants devastated the densely populated Gaza Strip and forced countless Israelis to rush to bomb shelters.