British national 'killed in Gaza'
The Foreign Office is investigating reports that a British national has been killed in Gaza.
A spokesman said UK officials were looking into reports that the person was killed in Rafah on Sunday.
The prime minister said he was "extremely concerned" by the reports.
Around 1,800 Palestinians, most of them civilians, are said to have been killed in Gaza since the conflict with Israel escalated in July. Sixty-seven Israelis have died, all but three soldiers.
A Thai national working in Israel was also killed.
A Foreign Office spokesman said: "We are aware of the reports of the death of a British national in Rafah and are urgently looking into them."
A seven-hour "humanitarian window" announced by Israel in parts of Gaza has ended - it did not include Rafah.
David Cameron said UK officials were doing everything they could to find out exactly what happened regarding the Briton who was reportedly killed.
"I don't want to say anything before we do that," he said.
"But this only reinforces the need for an immediate, unconditional, humanitarian ceasefire observed properly by both sides. This slaughter, this killing has got to end."
Shadow foreign secretary Douglas Alexander said reports of the death of a British aid worker only confirmed that "suffering continues".
He said the killing of civilians and children in Gaza in recent days represented "both a moral failure and a strategic error".
"Hamas displays no regard for human life and must cease firing rockets into Israel and digging tunnels to facilitate the murder of civilians," Mr Alexander added.
"But sustainable security for Israel cannot be achieved simply by permanent blockade, aerial bombardment and periodic ground incursion."
Meanwhile, International Development Secretary Justine Greening announced the UK is to provide a further £2m in emergency aid for Gaza.
The funds will help provide mattresses, blankets, nappies, cooking equipment and other essential supplies for nearly 8,000 families who have fled the conflict.
It will go to the United Nations Relief and Works Agency's (UNRWA) Gaza flash appeal. and brings the UK's total funding for Gaza to £15m.
On Monday, Prime Minister David Cameron said there had been "an appalling loss of life" in the region.
He also said the UN was right to speak out against an Israeli attack near a UN-run school in Gaza on Sunday, which Palestinian officials said killed at least 10 people.
UN Secretary General Ban Ki-moon called the attack "a moral outrage and a criminal act".
Mr Cameron said the UK government had been "very clear that there needs to be an immediate, comprehensive, humanitarian ceasefire and that we want this conflict to stop - and we obviously think that it's an appalling the loss of life".