Israel has bombed supply tunnels in the southern Gaza Strip in a second day of intense air raids aimed at forcing Hamas militants to halt rocket fire. A major tunnel bringing fuel into Gaza from Egypt was among three destroyed, Palestinians say. But Israel says its jets bombed more than 40 tunnels. Israel has also threatened to launch a ground assault and is now calling up 6,500 army reservists. Palestinians say at least 280 people have died in the air raids. Israel accuses Palestinian militants of using the tunnels to smuggle weapons into Gaza. As jets pounded the southern Gaza Strip hundreds of Palestinians stormed over a fence on the Gaza-Egypt border, but Egyptian security forces prevented them entering the country. Egyptian security forces fired shots and several injuries were reported.