Israel’s two strikes on Nasser Hospital are part of a pattern that has run the length of the war, monitors say.

Israel has killed 20 people, including journalists and health workers, in a strike on Nasser Hospital in the southern Gaza Strip.

In fact, it was two strikes that hit the hospital in Khan Younis on Monday 10 minutes apart about 10am (07:00 GMT).

Israeli Prime Minister Benjamin Netanyahu said in a statement released in English only that Israel deeply regretted what he characterised as a “tragic mishap” without explaining how Israel had hit the same hospital not once but twice in apparent error.

So what is a double-tap strike? Is it legal? Here’s what we know: