The contentious Israeli-backed group distributing food in Gaza closed its sites on Wednesday, a day after Palestinians trying to get supplies came under Israeli fire near one of the organisation’s aid centres.

The group, the Gaza Humanitarian Foundation, said that its four centres would be shut until Thursday to work on "organisation and efficiency" to better prepare for the huge numbers of Palestinians who have traveled to the sites since operations began more than a week ago.

The foundation added that Israeli troops were doing their own preparations along access roads leading to the distribution centres, without specifying what that entailed.

The Israeli military warned Palestinians not to approach the sites or the adjacent roads, saying that they were now considered "combat zones".

The pause in operations followed days in which dozens of Palestinians trying to reach one of the foundation's sites in the southern Gaza city of Rafah were killed after coming under fire, according to local health workers.

On Tuesday, the Red Cross and Gaza officials said that at least 27 people had died in the second large-scale deadly shooting in recent days. The Gaza Humanitarian Foundation said that a number of civilians had been killed in an area outside the site but did not provide a number. According to the Red Cross: "The majority of cases suffered gunshot wounds. Again, all responsive patients said they were trying to reach an assistance distribution site."

The Israeli military said its forces had opened fire roughly a third of a kilometre from the distribution site after they identified "several suspects moving toward them" away from the Israeli-designated access route. After they failed to respond to warning shots, troops fired "near a few individual suspects", the military said.

Brigadier General Effie Defrin, the Israeli military's chief spokesman, later suggested that the casualty numbers from the incident were inflated but did not provide an alternate toll. He said the Israeli military was investigating. On Sunday, more than 20 Palestinians were killed near an aid site, according to Gaza health officials.

The deadly incidents have further ensnarled the Israeli-backed aid effort, which has come under severe international criticism since its inception.

Hunger has become widespread in Gaza after an 80-day Israeli blockade on food, fuel, medicine and other supplies. The Israeli government began relaxing those restrictions last month and allowed some aid to enter the enclave, much of which has been destroyed during the war.

Israel has said that the new aid distribution system, with sites located in areas secured by Israeli troops and overseen mainly by US contractors, would prevent the supplies from falling into the hands of Hamas. The UN, however, says there is no evidence that Hamas systematically diverted international aid under the previous UN-coordinated distribution programme.

The UN and other aid groups have boycotted the initiative and have warned that it could endanger Palestinian civilians by forcing them to travel on foot through a war zone.