Heavy fighting rocked besieged Gaza on Wednesday as aid agencies warned of looming famine and new talks were held in Cairo towards an Israel-Hamas ceasefire and hostage release deal.

The White House sent Middle East envoy Brett McGurk for renewed talks involving mediators and Hamas, a day after a United Nations Security Council resolution calling for a ceasefire was blocked by the US.

An Israeli minister said the talks had raised the "possibility of progress".

Stricken by drought and depleted by upstream dams, Iraq's once mighty rivers the Tigris and Euphrates are suffocating under pollutants from sewage to medical waste.

In a country where half the population lacks access to safe drinking water, according to UN figures, state institutions are to blame for a man-made disaster which is turning rivers into waste dumps.

"What is strange about water pollution in Iraq is that most government institutions are responsible for it," Khaled Shamal, the ministry of water resources spokesman, told AFP.

Rockets at dawn, gunfire outside, hours of anxiety: a survivor of the October 7 attack shared his account of the day Gaza militants stormed his southern Israeli community, speaking into a video camera.

Arnon Avni's story is one of several hundred witness accounts of the deadly Hamas attack being collected by Israel's national library in partnership with local and international initiatives.

G20 foreign ministers open a two-day meeting Wednesday in Brazil, with the outlook bleak for progress on a thorny agenda of conflicts and crises, from the Gaza and Ukraine wars to growing polarization.

US Secretary of State Antony Blinken and Russian Foreign Minister Sergei Lavrov are both expected in Rio de Janeiro for the first high-level G20 meeting of the year -- though not China's Wang Yi.

An Israeli ground offensive in Rafah would turn the southern Gaza city into a "graveyard" and heighten the looming risk of famine, leaders of global humanitarian groups warned on Tuesday.

"The consequences of a full scale assault on Rafah are truly unimaginable," Avril Benoit, executive director of Doctors Without Borders (Medecins Sans Frontieres) in the United States, told reporters.

"Carrying out a military offensive there would turn it into a graveyard," Benoit said at a press briefing by MSF, Refugees International, Oxfam, Amnesty International and other groups.

UN aid agencies said Tuesday that food deliveries to war-torn northern Gaza had been suspended after looting attacks and that dozens of patients in a besieged hospital remain trapped in "indescribable" conditions.

The World Food Programme (WFP) and World Health Organisation (WHO) stepped up warnings as Israel prepares a major offensive in the southern city of Rafah.

The WFP said it resumed deliveries to northern Gaza on Sunday after a three-week halt but its first convoy "faced complete chaos and violence".

The French navy has shot down two drones over the Red Sea where Yemen's Huthi rebels have been attacking ships, the defence ministry in Paris said Tuesday.

The navy, which has two frigates deployed in the area, detected "multiple drone attacks originating in Yemen" overnight Monday to Tuesday, before destroying two of the unmanned aircrafts, the ministry said.

The attack came a day after the European Union formally launched a naval mission to protect Red Sea shipping from the Iran-backed Huthis who control much of war-torn Yemen.

Julian Assange, the 52-year-old Australian fighting extradition from Britain to the United States, is for some a fearless campaigner for press freedom. For others, he was reckless with classified information, possibly endangering sources.

Assange is the figurehead of the whistleblowing website that exposed government secrets worldwide, notably the explosive leak of US military and diplomatic files related to the wars in Iraq and Afghanistan.

Israel kept up its deadly bombardment of war-torn Gaza on Tuesday as Washington vetoed a UN Security Council resolution that called for a ceasefire in the Palestinian territory, where concern mounted about a growing humanitarian crisis.

Global powers trying to navigate a way out of the spiralling crisis have come up short, with a so-far fruitless push by mediators to reach a truce and two rival ceasefire proposals put forward at the United Nations.

The United States vetoed a UN Security Council resolution on Tuesday that called for an immediate ceasefire in Gaza, drawing stern criticism from allies as President Joe Biden faces mounting pressure to temper support for Israel.

Washington had circulated its own, alternative draft resolution ahead of the vote. Unlike past US efforts, that version does feature the word "ceasefire" -- but with no call for it to be enacted immediately.