GAZA/JERUSALEM (Reuters) - Israeli forces killed 10 Palestinian militants who slipped across the border from Gaza through hidden tunnels on Monday, the military said, as the death toll from the two-week conflict passed 500 amid growing international calls for an end.

Defying a U.N. Security Council appeal for an immediate ceasefire, Israeli jets, tanks and artillery continued to pound the Gaza Strip, killing 28 members of a single family near the enclave's southern border with Egypt, medics said.

The Islamist group Hamas and its allies fired multiple missiles across southern and central Israel, and heavy fighting was reported in the north and east of Gaza.

Non-stop attacks lifted the Palestinian death toll to 496, including almost 100 children, since fighting started on July 8, Gaza health officials said. Israel says 18 of its soldiers have also died along with two civilians.

Despite worldwide calls for a cessation of the worst bout of Palestinian-Israeli violence for more than five years, Israeli ministers ruled out any swift truce.

"This is not the time to talk of a ceasefire," said Gilad Erdan, communications minister and a member of Israeli Prime Minister Benjamin Netanyahu's inner security cabinet.

"We must complete the mission, and the mission cannot end until the threat of the tunnels is removed," he told reporters.

For its part, Hamas, weakened by the loss of Egypt and Syria as allies, voiced determination to fight on to break Israel's economic siege of Gaza.