Israeli troops and armor pushed deeper into northern and central Gaza earlier on Monday, as the UN and medical staff warned that airstrikes are hitting closer to hospitals where tens of thousands of Palestinians have sought shelter alongside thousands of wounded.

A video on social media showed an Israeli tank and bulldozer in central Gaza blocking the territory’s main north-south highway, which the Israeli military earlier told Palestinians to use to escape the expanding ground offensive.

The video captured the moment a car approached an earth barrier across the road. The car stops and turns around. As it heads away, the Israeli tank opens fire, and an explosion engulfs the vehicle. The Gaza Health Ministry later said three people were killed in the attack.

When asked whether forces had positioned on the road, Israeli military spokesman Rear Adm. Daniel Hagari said, “we expanded our operations” but would not comment on specific deployments.

The Israeli advances had put their forces on both sides of Gaza City and the surrounding areas of northern Gaza in what Prime Minister Benjamin Netanyahu called a “second stage.”

However, the head of the Hamas Government Media Office, Salama Marouf, has said the presence of army tanks and a bulldozer was only an incursion through open agricultural land.

“These vehicles targeted two civilian cars on Salah al-Din Street and bulldozed the street before the resistance forced them to retreat,” the Palestinian group controlling the Gaza Strip said in a statement.

“There is currently no presence of [Israeli] occupation army vehicles on Salah al-Din Street, and civilian movement has returned to normal.”

Hamas also said the Israeli army is trying to “paint an unrealistic picture of the presence of its soldiers in areas inside the Strip.”

Hundreds of thousands of Palestinians remain in the north and would no longer be able to escape if the north-south highway is blocked.

Around 117,000 displaced people are staying in hospitals in northern Gaza, alongside thousands of patients and staff, hoping they will be safe from strikes, according to UN figures.

Most residents heeded Israel’s orders to flee to the southern part of the besieged territory, but many stayed in part because Israel has also bombarded targets in so-called safe zones.

Meanwhile, relief workers said the largest convoy of humanitarian aid to arrive in Gaza still fell far short of needs.

Israel has killed over 8,000 people, mostly children, in Gaza, according to the Health Ministry.