The UN human rights agency on Monday condemned Israel's targeted killing of six journalists in Gaza as a "grave breach of international humanitarian law".

The office of UN High Commissioner for Human Rights Volker Turk said on X that the Israeli military had targeted a tent housing five staff from Qatari broadcaster Al Jazeera.

A freelance journalist was also killed in Sunday's strike, which Israel has acknowledged was a planned operation.

"Israel must respect and protect all civilians, including journalists," Turk's office added, noting that at least 242 Palestinian journalists have been killed in Gaza since the Hamas attacks on Israel set off war in the Palestinian territory in October 2023.

"We call for immediate, safe and unhindered access to Gaza for all journalists," it said.

The Israeli military confirmed it had targeted prominent reporter Anas al-Sharif, whom it has repeatedly labelled a "terrorist" affiliated with Hamas, saying he "posed as a journalist".

Reporters Without Borders, a media freedom group, said it "strongly and angrily condemns the acknowledged murder by the Israeli army" of al-Sharif and the other journalists.

The press freedom campaign group said he was "one of the most famous journalists from the Gaza Strip [and] the voice of the suffering Israel has imposed on Palestinians in Gaza".

Al-Sharif, 28, was one of Al Jazeera's most recognisable faces working on the ground in Gaza, providing daily reports in regular coverage.

He was killed alongside fellow correspondent Mohammed Qreiqeh and camera operators Ibrahim Zaher, Mohammed Noufal and Moamen Aliwa, Al Jazeera said.

The Israeli military said it had targeted al-Sharif, saying he "posed as a journalist" but was in fact "the head of a terrorist cell... responsible for advancing rocket attacks against Israeli civilians and IDF troops."

Reporters Without Borders called the Israeli allegations "baseless". (AFP)