Tank shelling on a UN shelter on Wednesday killed nine people in Gaza's main southern city of Khan Yunis, said the Gaza head of the UN agency for Palestinian refugees.

"Two tank rounds hit building that shelters 800 people - reports now 9 dead and 75 injured," Thomas White, UNRWA's Gaza director, said on X, formerly Twitter.

The head of UNRWA, Philippe Lazzarini, condemned the attack and said the number dead was likely to rise, as reported by GulfNews.

"Once again a blatant disregard of basic rules of war," Lazzarini said on X.

He added that the compound had been clearly marked as a UN facility and its coordinates shared with Israeli authorities, without specifying responsibility for the shelling.

Israeli air strikes and ground operations were focused on Thursday on the Gazan city of Khan Yunis, where the UN said nine people were killed by tank shelling at one of its shelters the day before.

The deadly incident came after the Israeli army said it had encircled the city, where footage released by the military showed soldiers engaged in urban combat amid ruined buildings.

Hamas's press office also reported fierce clashes in the centre and west of Khan Yunis, while its health ministry counted multiple deaths overnight from strikes in the city and elsewhere in the territory.

It said four children were killed in the Nuseirat camp in an early morning bombardment on Thursday.

Wednesday's attack on the UN shelter for displaced people saw the site hit by two tank rounds, killing nine and injuring 75, said Thomas White, the Gaza head of the UN agency for Palestinian refugees, UNRWA.

UNRWA chief Philippe Lazzarini said the number of dead was likely to rise.

James McGoldrick, interim UN humanitarian coordinator for the Palestinian territories, told reporters that "buildings were ablaze" at the shelter in the aftermath of the strike.

When asked about the incident, the Israeli army told AFP "a thorough review of the operations of the forces in the vicinity is underway", adding it was examining the possibility that the strike was a "result of Hamas fire".