(AFP) - Israeli tanks briefly advanced Monday into the fringes of Gaza City, witnesses said, as the army ramped up its war on Hamas saying it had killed dozens of militants in hundreds of strikes.

The military said it had struck more than 600 targets in 24 hours, up from 450 the previous day, in one of the most intense days of the conflict unleashed when Hamas militants crossed into Israel on a killing rampage on October 7.

"Dozens" of tanks entered the Zaytun district in south of the Palestinian territory's main city, cutting a key road from the north to the south of the Gaza Strip for more than an hour, witnesses told AFP journalists in southern Gaza by phone.

"They have cut the Salahedin road and are firing at any vehicle that tries to go along it," said one resident who did not want to be identified.

Israeli jets bombed a section of the road leaving large craters, another resident said.

Video footage obtained by AFP showed a tank blowing up one car on the road.

The tanks stayed for just over an hour and cars soon returned to the highway, driving onto the verge in the parts where craters made the road unusable, residents said.

The military wing of Hamas said it had fired anti-tank missiles at two Israeli armoured vehicles.

The Hamas government press service played down the importance of the incursion, however.

It said Israel was seeking to give a "false image that its soldiers are present in the Gaza Strip interior, even though blows delivered by the resistance have prevented them".

- Buildings razed -

Zaytun has about 130,000 inhabitants -- out of a total Gaza population of 2.4 million -- but the zone where the tanks went is relatively sparsely inhabited.

Dozens of buildings west of the Salahedin road have already been demolished in Israeli strikes.

The strikes have also razed at least 10 high-rise buildings in Tal al-Hawa, a district in southwest Gaza City, and damaged a Turkish-funded cancer hospital in the same area, its director Sobhi Skeik told AFP.

Israeli forces have since Friday stepped up a ground offensive seen as a key part of the military response to the October 7 Hamas attacks that Israeli officials say killed 1,400 people.

Israel says Hamas gunmen also seized at least 239 hostages.

The health ministry in Hamas-run Gaza on Monday said more than 8,300 people -- over half of them women and children -- have been killed in Israeli air and ground strikes.

Israel has repeatedly warned the 1.1 million people in northern Gaza, including Gaza City, to head south to avoid its military strikes.

The Israeli army said night-time raids had killed "dozens" of militants "inside buildings and tunnels".

In one raid, a fighter jet targeted a building "with over 20 Hamas terrorist operatives inside", the military said.

Another fighter jet struck an anti-tank missile launching post around Al-Azhar University in the heart of Gaza City.

The army said it had hit "weapons depots, dozens of anti-tank missile launching positions, as well as hideouts and staging grounds used by the Hamas terrorist organisation".

© Agence France-Presse