If there's no way to corroborate or refute what Israel said, don't print what Israel said.
Why? What they said is newsworthy.
"Israel bombed this building"
"Why?"
"Dunno, didn't ask."
Even if you don't believe the answer, getting an answer is still newsworthy. Everyone should be aware that it's not necessarily the truth, but it's newsworthy as the justification they're using. If it comes out later that the building was an orphanage, you can't use that to challenge the government's justification that it was a command and control center if you never got them on the record saying they bombed it because it was a command and control center.