The United Nations' head of relief says negotiations are underway to open another crossing into the Gaza Strip, allowing the flow of vital aid to war-torn Palestinians.

The situation in the enclave is growing increasingly dire as Israeli forces continue their offensive.

Under-Secretary-General for Humanitarian Affairs Martin Griffiths says there are "promising signs" the Kerem Shalom crossing between Gaza and Israel may open soon, adding that it would be a "huge boost to the logistical process."

The UN agency says the crossing accounted for more than 60 percent of the goods that flowed into Gaza before October's dramatic escalation in violence.

Israeli troops are intensifying their attacks. Military officials say they struck about 450 targets across Gaza on Thursday and Friday, including in the main southern city of Khan Younis.

The Israelis believe Hamas' leader in Gaza, Yahya Sinwar, may be hiding in the city.

Aid supplies have been brought into the enclave via the Rafah crossing, but there is not enough to go around.

One displaced woman said, "We have no shelter, no toilets and no water. It's impossible to set up a tent. We don't even have anything to cover our children when they sleep."

The Jewish festival of Hanukkah began on Thursday. People in Tel Aviv were seen lighting 138 candles, one for each of those still being held captive by Hamas.

The grandson of one hostage urged the global community to do more to help bring about their release.