The Israeli army has enlarged ground operations on Thursday into Gaza City as its air and ground military offensive goes on for the 20th successive day, residents in the city and medics said.

Residents of Gaza City said several Israeli army tanks and armored vehicles backed by warplanes carried out a larger incursion into the southern Gaza City neighborhood of Tal el-Hawa.

They said that during the incursion, the tanks shelled al-Quds Hospital, which belongs to the Palestinian Red Crescent, adding they saw flames of fire and black smokes coming out from inside the hospital.

"There are 500 patients, nurses and paramedics in the hospital and until now we don't know what's their fate," said Dr. Omer el-Azayza, director of al-Quds Hospital in southern Gaza City.

"It seems that the Israeli army had decided to target hospitals and journalists offices after it had targeted homes, mosques and cemeteries and killed hundreds of innocent children and women," said Walid Abu Jabal, a 35-year-old Gaza resident.

UN communication chief in Gaza Sami Mesha'sha said in a statement that Israeli tank shells destroyed the area around Gaza UN main headquarters, adding that one shell landed in the UN headquarters' yard.

Meanwhile, two Palestinian militants were killed in the ground fighting with Israeli soldiers, medics in Gaza said, adding that 23 Palestinians were killed since early Thursday morning.

The Israeli army expanded ground operations into the Gaza Strip and beefed up more tanks and armored vehicles into south and southeast Gaza City amid intensive gunfire and tank shelling.

Pillars of black smoke are still seen coming out from different targeted buildings, houses and cars in the neighborhood of Tal el-Hawa, while sounds of bombs and explosions can be clearly heard in the city.

Residents said that dozens of Israeli army tanks and armored vehicles left dozens of houses under their full control, and had fired dozens of tank shells at those houses, causing lost of casualties and panic among the population.

Several residents were calling on urgent help through local radio stations, as they were inside their houses with so many casualties, where ambulances and rescue teams were not able to reach the area due to heavy shelling.

Witnesses said that the Israeli tanks occupied the main street of Tal el-Hawa and seized the park called "Barcelona" which was built by Spain several years ago.

Gaza emergency chief Mo'aweya Hassanein said that since the beginning of the offensive almost three weeks ago, 1,060 Palestinians were killed, adding that 21 bodies were received on Thursday at Gaza hospitals.

Meanwhile, Islamic Hamas movement's armed wing al-Qassam Brigades announced on Thursday that its militants had carried out a series of rockets attacks on Israel, as well as attacking Israeli army tanks and vehicles.