The relevant Editorial Guideline states:
We must report acts of terror quickly, accurately, fully and responsibly. Our credibility is undermined by the careless use of words which carry emotional or value judgements. The word "terrorist" itself can be a barrier rather than an aid to understanding. We should try to avoid the term without attribution. We should let other people characterise while we report the facts as we know them.
We should not adopt other people's language as our own. It is also usually inappropriate to use words like "liberate", "court martial" or "execute" in the absence of a clear judicial process. We should convey to our audience the full consequences of the act by describing what happened. We should use words which specifically describe the perpetrator such as "bomber", "attacker", "gunman", "kidnapper", "insurgent, and "militant". Our responsibility is to remain objective and report in ways that enable our audiences to make their own assessments about who is doing what to whom.