Israeli troops appeared to have encircled the east of Rafah in Gaza as tanks were seen on the road bisecting the densely populated city from east to west.

The Israel Defense Forces (IDF) are pressing on with their operation against Gaza’s last largely intact city as aid organisations warned of catastrophically dwindling supplies because of the closing of the main crossing point into Gaza.

Israeli tanks captured the main road dividing Rafah’s east and west on Friday morning, according to local journalists.

Residents of western Rafah said they were hearing near-constant bombing as Israeli troops apparently engaged with Hamas fighters there.

Earlier on Friday, artillery strikes on Rafah were reported a day after Joe Biden, the US president, threatened to suspend the supply of bombs and other weapons to Israel if a full-scale offensive in Gaza’s last city largely unaffected by heavy fighting were to go ahead.

A resident of Tel al-Sultan in the west of Rafah said Israeli tanks were three or four miles away and that everywhere in Rafah was being targeted with airstrikes.

On Friday, Israeli troops fought at close quarters with groups of Hamas fighters, killing several, according to the IDF.

Hamas said its forces ambushed Israeli tanks near a post in the east of Rafah, which would mean the IDF went in several miles from the east to the outskirts of the city’s build-up area.

Heightened IDF activity in Rafah followed the war cabinet’s decision in early hours on Friday to expand the operation, according to Israeli media outlets.

Ministers at a late-night session agreed on a “measured” expansion of fighting that would not cross the red lines indicated by the United States that could trigger a suspension of weapons supplies to Israel, the Yedioth Ahronoth newspaper reported.

Mr Biden has repeatedly said the US would oppose an IDF operation in Rafah but when first Israeli tanks were sighted at the Rafah crossing with Egypt, capturing the key site, he made it clear that the assault did not go as far as to cross the red line for Washington.

The United Nations and major aid groups raised the alarm about an even worse humanitarian calamity unfolding in Gaza as the Rafah crossing that processed aid going into the enclave remained shut.

Aid operations would grind to a halt “within days” unless the crossing with Egypt, shut down after Israel captured it on Monday, re-opens, the UN warned.

The UN’s World Food Programme will run out of food for distribution in southern Gaza by Saturday unless more aid arrives, Georgios Petropoulos, an official for the UN Office for the Coordination of Humanitarian Affairs (OCHA) working in Rafah, said.

He said about 30,000 people were leaving Rafah daily in search of safety, but that humanitarian workers had no supplies to help them set up camp in a new location.

Other UN agencies warned about an inevitable human toll of an extended operation in densely populated Rafah.

“For five days, no fuel and virtually no humanitarian aid entered the Gaza Strip, and we are scraping the bottom of the barrel,” Hamish Young, Unicef’s senior emergency coordinator in the Gaza Strip, said.

“Let’s be very clear this will result in children dying. Deaths that can be prevented.”