allegation v. accusation v. claim

[hhtt]

"A Huwei executive and a former Polish state security officer have been arrested in Poland on allegation of spying for China's secret service, raising fresh questions for the telecoms group amid global scrutiny of its connections with the Chinese state."

Would you please explain why is the present perfect used in the above sentence?

Source: FT Weekend Saturday 12 January/Sunday 13 January 2019.

Above is the original but I am having trouble understanding the differences between "allegation", "accusation", and "claim". Would you please explain the most basic differences between these words?

Allegation:

A claim or assertion that someone has done something illegal or wrong, typically one made without proof

allegation | Definition of allegation in English by Oxford Dictionaries

Accusation:

A charge or claim that someone has done something illegal or wrong.

accusation | Definition of accusation in English by Oxford Dictionaries

Claim:

reporting verb State or assert that something is the case, typically without providing evidence or proof.

claim | Definition of claim in English by Oxford Dictionaries

Thank you very much.

 

[PaulQ]

In broad terms:

A claim is any statement that the speaker says is true. If I say "My cat has 15 legs" - then that is my claim - I am telling you, as a fact, that my cat has 15 legs. Equally, "My cat is male" is a claim. A claim does not require evidence to be a claim, but evidence may be requested. Claims can be positive, negative or neutral

Allegations and accusations are both types of claim.

An allegation is weaker than a claim in its intensity. It is usually a claim with little or no substantial evidence to the effect that something has happened, or that someone has done something. The speaker makes no claim that the statement is true. In fact, allegations are usual similar to rumours. "The allegation is that when he was in Africa he had five wives." "The allegation is that when he was in Russia he discovered a gold mine." Allegations can be positive, negative or neutral

An accusation is a claim usually with some evidence (the evidence may be good or bad evidence), in which the speaker claims that a named person has committed a criminal act or taken part in shameful or immoral behaviour. Accusations are always negative.

 

[kentix]

Claim is more general. If you claim someone has committed a crime that's an allegation.

Accusation tends to be used in more personal circumstances and not necessarily about crime. If you are mad at me for something you say I did you might make an accusation against me. "You ate my sandwich after I told you not to." Few people would call that an allegation, even though you could say it that way.