The UN's human rights office has condemned a targeted Israeli attack that killed six journalists in Gaza, calling it a grave breach of international law.

Five Al Jazeera journalists, including correspondent Anas al-Sharif, were killed in an Israeli air strike on Sunday. Two others were killed, including a freelance journalist, the broadcaster said.

Israel's military said it targeted Sharif, alleging he had "served as the head of a terrorist cell in Hamas" - something Sharif denied. Israel provided little evidence.

The BBC understands Sharif did some work with a Hamas media team in Gaza before the current conflict.

In social media posts before his death, the journalist is heard criticising Hamas.

Media rights groups and countries, including Qatar, condemned the attack.

UK Prime Minister Sir Keir Starmer's spokesman said the UK government was "gravely concerned" and called for an independent investigation.

Speaking to reporters, Starmer's official spokesman said Israel should ensure journalists can work safely and report without fear.

The funerals of Sharif, fellow Al Jazeera correspondent Mohammed Qreiqeh, and cameramen Ibrahim Zaher, Mohammed Noufal and Moamen Aliwa took place on Monday following the targeted missile strike on their tent in Gaza City.

Mohammad al-Khaldi was named by medics at al-Shifa hospital as the sixth journalist who was killed during the strike, Reuters news agency reported. Another person was also killed in the attack, it said.

Streets in Gaza were thronged with crowds gathered for the funerals. Anas al-Sharif was a household name who had millions of followers online.

Reporters Without Borders, a media freedom group, strongly condemned what it called the assassination of Sharif.

The Foreign Press Association said it was outraged by the targeted killing. It said the Israeli military had repeatedly labelled Palestinian journalists "as militants, often without verifiable evidence".

The Committee to Protect Journalists (CPJ) said it was appalled by the attack and that Israel had failed to provide evidence to back up its allegations against Sharif.

"Israel has a longstanding, documented pattern of accusing journalists of being terrorists without providing any credible proof," the organisation added.

The Israeli military has suggested it has documents found in Gaza that confirmed Sharif belonged to Hamas.

It said these include "personnel rosters, lists of terrorist training courses, phone directories and salary documents".

The only materials that have been released for publication are screenshots of spreadsheets apparently listing Hamas operatives from the northern Gaza Strip, noting injuries to Hamas operatives, and a section of what is said to be a phone directory for the armed group's East Jabalia battalion.

The BBC cannot independently verify these documents, and has seen no evidence of Sharif having involvement in the current war or remaining an active member of Hamas.

No Israeli explanation has so far been given for the killing of the entire Al Jazeera news crew.

CPJ says at least 186 journalists have been killed since the start of Israel's military offensive in Gaza in October 2023 - the deadliest period for journalists since it began recording such data in 1992.

"Israel must respect & protect all civilians, including journalists," the UN Human Rights office said in a post on X. "We call for immediate, safe and unhindered access to Gaza for all journalists."

Last month, the BBC and three other news agencies - Reuters, AP and AFP - issued a joint statement expressing "desperate concern" for journalists in the Gaza Strip, who they say are increasingly unable to feed themselves and their families.

The Israeli government does not allow international news organisations, including the BBC, into Gaza to report freely, so many outlets rely on Gaza-based reporters for coverage.

Meanwhile, in Gaza, five more people have died from malnutrition in the past 24 hours, including one child, according to the Hamas-run health ministry.

This brings the total number of malnutrition deaths to 222, including 101 children, the health ministry said.

The UN's humanitarian agency said on Friday that the amount of aid entering Gaza continues to be "far below the minimum required to meet people's immense needs". Last month, UN-backed global food security experts warned that the "worst-case scenario of famine is currently playing out".

Israel has continued to deny that there is starvation in Gaza and has accused UN agencies of not picking up aid at the borders and delivering it.

The UN's humanitarian agency has said it continues to see impediments and delays as it tries to collect aid from Israeli-controlled border zones.

Israel launched its offensive in response to the Hamas-led attack on southern Israel on 7 October 2023, in which about 1,200 people were killed and 251 others were taken hostage.

Since then, 61,430 people have been killed in Gaza as a result of Israel's military campaign, according to the health ministry.