The Israeli military bombarded the Gaza Strip on Tuesday, pushing the total death toll to nearly 600. The latest attacks left plumes of black smoke in the sky over the coastal enclave as ground troops continued their offensive, which Israel has announced is aimed at destroying tunnels used by the militant group Hamas, as well as sites used for launching rockets.

Most of those killed by Israel during its bombardment of the Gaza strip have been civilians, including more than 120 children. A further 900 children have been injured, according to the UN Children's Fund (UNICEF).

Among those reported killed on Tuesday were seven German citizens. A spokesman for the German Foreign Ministry told the DPA news agency that it had indications that all of the members of a German-Palestinian family had been killed in an attack on a building on Gaza City on Monday night. The dead included both parents and five children aged 4 to 12.

The father and mother had spent years living and working in Germany and all seven were citizens. The family had returned to the Palestinian Territories 13 years ago.

Militants, meanwhile, continued to fire rockets at Israel on Tuesday, with at least one triggering air raid sirens in Tel Aviv, while another hit near Ben Gurion International Airport.

Humanitarian situation worsens

"There is literally no safe place for civilians," said UN Office for Humanitarian Assistance (OCHA) spokesman Jens Laerke during a briefing in Geneva on Tuesday.

Nearly 500 homes have been destroyed by Israeli airstrikes in Gaza and 100,000 people have been displaced.

More than 1.2 million of Gaza's 1.7 million people have no or only limited access to water.

"In addition, we do have reports of sewage flooding which is a threat to public health," Laerke said.

Attempts by US Secretary of State John Kerry and UN Secretary-General Ban Ki-moon, who were both in the region on Tuesday, appeared to have little prospect of immediate success, with both Israel and Hamas expressing determination to continue fighting.

pfd/mkg (AFP, Reuters, dpa, AP)