Steve, Channel 4 News last night.
The reporter in Gaza said Israel had warned residents in an area to leave because attacks were imminent, but Hamas came on the radio and told them to stay put because it was just "propaganda."

Any country subject to bombardment from outside is quite legally entitled to strike back.
It is illegal for either side to fight from civilian occupied areas.

Hamas commits a war crime by launching missiles at civilian targets.
It commits another by failing to evacuate civilians from its weapons sites.

It is not illegal to strike at targets protected by living sandbags, provided warnings are given and efforts are made to minimise civilian casualties.
Hamas chooses not to move its people to safety as it is legally required to do.