What is this よう doing behind the verb?


For full context:
<https://www3.nhk.or.jp/news/html/20180306/k10011353421000.html?utm_int=news_contents_news-
main_001>

The sentence in question:
新燃岳で爆発的な噴火が起きたのは、７年前の平成２３年以来で、気象庁は、噴火警戒レベル３を継続し、大きな噴石や火砕流に警戒する **よう**
呼びかけています。

I would translate the part surrounding よう as "...they called out that one
shall pay attention to great cinders and pyroclastic flow." But I never saw よう
used in this way.




without よう it's incomplete. よう used to connect two parts of sentence like "to"
in English, in "asked to do" form.

