It's consistent with the way other movies have been rated in the past.
It feels like a 12A. Whether an under 12 really is unready to see it I don't know though. Pretty brutal for them I'd think but not traumatizing.

12 or pg.
There was no difference between this and war of the world's. We don't see any violence, I didn't hear any swearing nor did I see any sex. The most violent scene was someone being shot OFF SCREEN we don't actually see anything.

I just watched it without looking at the certificate on the cover and thought it'd be a 15 as very intense, shocking, horror (but PG13 in states as not enough swearing) normally PG13 equals 12A but sometimes is a 15.