Condemnations poured in from the UN and media rights groups Monday after an Israeli strike killed an Al Jazeera news team in Gaza, as Palestinians mourned the journalists.

Dozens of Gazans stood amid bombed-out buildings in the courtyard of Al-Shifa Hospital in Gaza City to pay their respects to Anas al-Sharif, a prominent Al Jazeera correspondent aged 28, and four of his colleagues killed on Sunday.

Hospital director Mohammed Abu Salmiya said a sixth journalist, freelance reporter Mohammed al-Khaldi, was killed in the strike that targeted the Al Jazeera team.

Al Jazeera said four other employees — correspondent Mohammed Qreiqeh, and cameramen Ibrahim Zaher, Mohammed Noufal and Moamen Aliwa — were killed when the strike hit a tent set up for journalists outside the main gate of Al-Shifa.

According to local journalists, Sharif had worked at the start of his career with a Hamas communication office, where his role was to publicise events organised by the group that has ruled the Gaza Strip since 2006.

Sharif was one of the Al Jazeera's most recognisable faces working on the ground in Gaza, providing daily reports on the now 22-month-old war.

Media freedom groups have condemned the Israeli strike on journalists, which the UN human rights agency called a "grave breach of international humanitarian law".

A posthumous message, written by Sharif in April in case of his death, was published online saying he had been silenced and urging people "not to forget Gaza".

In July, the Committee to Protect Journalists (CPJ) called for his protection following online posts by an Israeli military spokesman.

The group had accused Israel of a "pattern" of labelling journalists militants "without providing credible evidence", and said the military had levelled similar accusations against media workers in Gaza including Al Jazeera staff.

"International law is clear that active combatants are the only justified targets in a war setting," Jodie Ginsberg, CPJ's chief executive, told AFP Monday.

Unless Israel "can demonstrate that Anas al-Sharif was still an active combatant, then there is no justification for his killing", she said.

Al Jazeera called the attack "a desperate attempt to silence voices exposing the Israeli occupation", as it described Sharif as "one of Gaza's bravest journalists".

The Qatari broadcaster also said the strike followed "repeated incitement" and calls by Israeli officials to target Sharif and his colleagues.

Reporters Without Borders says nearly 200 journalists have been killed in the war on Gaza.

Israel prevents international reporters from entering Gaza, except on occasional tightly controlled trips with the military.

The strike on the news team in Gaza City came days after the Israeli security cabinet had approved plans to sent troops into the area, a decision met with mounting domestic and international criticism.

UN Secretary-General Antonio Guterres condemned the killing of Al Jazeera journalists, his spokesperson said Monday.

"The secretary-general calls for an independent and impartial investigation into these latest killings," said UN spokesperson Stephane Dujarric.

The European Union condemned the killing of five Al Jazeera journalists, the bloc's foreign policy chief Kaja Kallas said Monday.

"The EU condemns the killing of five Al Jazeera journalists in an (Israeli military) air strike outside Al-Shifa Hospital in Gaza City, including the Al Jazeera correspondent Anas al-Sharif," she said after EU foreign ministers discussed the war in virtual talks.

British Prime Minister Keir Starmer is "gravely concerned" about the repeated targeting of journalists in Gaza, his spokesperson said Monday.

Israel's offensive has killed at least 61,499 Palestinians, according to the health ministry in Hamas-run Gaza, figures the UN says are reliable.