A letter signed by more than 600 lawyers on Thursday placed more pressure on the UK government to suspend arms export licences to Israel after three Britons were killed in an Israeli strike.

The three died in Gaza on Monday along with four others who had all been working for US-based food charity World Central Kitchen (WCK).

Britain's strategic licensing criteria states that weapons should not be exported when there is a "clear risk" they could be used in international humanitarian law violations.

In the letter, signatories including former Supreme Court judges said the government risked breaching international law by continuing to allow the export of weapons to Israel.

They added that the worsening situation in Gaza and the International Court of Justice's conclusion that there was a "plausible risk of genocide" obliged to UK to suspend arms sales to the country.

London has approved over £487 million ($614 million) of weapon sales to Israel since 2015 in so-called single issue licences, while companies export more under open licences, according to arms control groups.

That includes contributing key equipment worth tens of millions of pounds for F-35 fighter jets made in the United States and sold to Israel, they say.

On Wednesday, two days after the Israeli strike killed the seven WCK staff, two UK opposition parties and various individual lawmakers renewed demands for the government to suspend the exports.

They included former UK national security adviser Peter Ricketts, who now sits in Britain's unelected upper chamber, the House of Lords.

Ricketts said there was "abundant evidence now that Israel hasn't been taking enough care to fulfil its obligations on the safety of civilians".

Prime Minister Rishi Sunak has so far appeared unswayed by the demands, telling The Sun tabloid Wednesday that London has a "careful export licensing regime".