(Reuters) - Israeli air strikes and artillery bombardments hit Khan Younis in the south of the Gaza Strip on Saturday as Israel pressed its offensive against Hamas militants with renewed force after the collapse of a truce in the nearly two-month-old war.
Palestinian residents said houses and open areas had been hit and three mosques destroyed in Khan Younis in the past hours. Columns of smoke were rising into the sky, Reuters journalists in the city said.
The Israeli military said that in the last 24 hours combined attacks by its ground, air and naval forces had hit 400 militant targets and killed an unspecified number of Hamas fighters.
Hamas media said about 200 Palestinians had been killed since the end of the truce - adding to the more than 15,000 dead in Gaza since the start of the war, according to health authorities in the enclave.
The warring sides blamed each other for the collapse of the seven-day truce, during which Hamas had released hostages in exchange for Palestinian prisoners held in Israeli jails.
The United Nations said the fighting would worsen an extreme humanitarian emergency.
"Hell on Earth has returned to Gaza," said Jens Laerke, spokesperson for the U.N. humanitarian office in Geneva.
The conflict broke out on Oct. 7 when Hamas militants crossed into southern Israel and killed 1,200 people, mostly civilians, in a rampage against kibbutzim and other communities. More than 200 hostages were taken back in Gaza.
Israel responded with a ferocious bombing campaign and a ground offensive which has destroyed large areas of Gaza and displaced hundreds of thousands of people in what has become the the bloodiest episode of the wider Israel-Palestinian conflict.
Friday saw intense bombing in Khan Younis and Rafah in the south, medics and witnesses said.
Displaced Gazans have been sheltering there because of fighting in the north of the densely populated enclave but residents said they feared Israel was preparing for ground troops to move on the south.
Leaflets dropped by Israel on eastern areas of Khan Younis ordered residents of four towns to evacuate - not to other areas in Khan Younis as in the past, but further south to Rafah.
"You have been warned," the leaflets said in Arabic.
Residents took to the road with belongings heaped up in carts, searching for shelter further west.